This will help you to visually understand what is Segwit how to use it and the story with B-Cash

If you understand some computer common sense and not a Crypto developer, and this one is for you.
If you are the people who is unable to reinstall your windows or mac, this is not for you.

--- IF you know who Bitcoin works jump to the youtube video part ---

I'm a newbi of Bitcoin. I'm a big fan of the following Crypto youtuber
like
Ivan on Tech, Boxmining, DataDash and Crypto Investor

They all have videos to explain what is segwit but No one made me understand
What really is segwit?
why Miner Don't like it?
why BCH is Segwit's Enemy?

And Now I finally seems to understand it, and I'll give you an easy to understand explanation.
but not accurate.

--- BTC is having network congestion ---
BTC network is slow (Block time) for security purpose.
after you transfer your BTC to someone or an exchange you will need a miner to put your transaction into a block.
only blocks will be record into the blockchain if something is on the blockchain it will be the legit history, and almost impossible to change.
BTC network controls that a new block will be created for roughly every 10 mins by adjust the mining difficulty for every 2000 Blocks.
every block is limited to 1MB in side and can contain let's say 1000 transactions (in old Legacy mode, I pick 1000 for you to easy to understand it's not fixed)
that's means if there is more than 1000 people is transfering money on BTC blockchain in this 10 mins time frame.
someone's transaction will not be recorded on the block chain.
The User of BTC will have to compete with each other by offering higher Mining fees to the miners.
Miners pickup the people they like, who offer them a nice fee and mine this more profitable 1000 transactions.
so. High BTC price attracts more people to use BTC, and the more congestions there is and the more of the mining fees.

Miners are happy. (Most of them are located in China)

--- Shame !!! ---
Once upon a time people says BTC are low fees. but nowadays transfer BTC to a guy next to you can be more expensive than international wire transfer.
It's a shame, and a slap on the face.

--- Developers want to lower the crazy fees ---
To Change the BTC network is crazy hard!
Because it's decentralized in nature. you have to make every node in the network to upgrade BTC software's version.
You are not the boss of BTC. you can't push down your BTC software and force upgrade.
and there is no election mechanism to make it even harder.

The Main BTC developers named: "Core" team.
They comes up with a clever solution (or hack) which named segwit.

----Segwit! the real meaning.----

I won't use other people's explain, which makes no sences to me. I use my own which will make it straight and understandable.
but not accurate.

Segwit is:
Rearrange the block structure and increase the block size to 4MB to squeeze more transactions into one block.
and the new 4MB block can cheat the old BTC nodes, and make the old BTC node to believe it still a normal 1MB block.
the extended 3MB will only be processed by Node that runs New BTC software and the old BTC software will ignore it but still believe it's a valid block and will not discard it.
and this will make Segwit backward compatible and increase to 4000 (just for you easy to understand) transactions per 10 mins.
the 3MB part is dynamic if all transactions are segwit it will be 3MB large, if all transaction are traditional the 3MB part will be 0.

so the extended block never existed. and signature is never removed. (If you watched other videos)
Signature is just relocated into the 3MB part at the end of each block.

--- Miners are not happy with Segwit ---
1st you need to understand How Miners charge you for your transaction?

Post office will charge you based on weight or by size.
Bankers will charge you based on percentage of your principals.
Miners will charge you based on how many words in your transaction sentence, and how many people are waiting.

like
TXID=1 time=21:00 A (address:xxxxxx) give B (address: bbbbbb) 1.0 Bitcoin (A Sign here: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)
TXID=2 time=22:00 C (address:cccccc) give B (address: bbbbbb) 9.9 Bitcoin (C Sign here: CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC)

As you can see
the above 2 transaction have same Number of words but different in value. Miner's charge them the same price.

But a Segwit transaction is looks like this in a block
TXID=3 time=21:00 S (address:3sssss) give B (address: bbbbbb) 1.0 Bitcoin (S Sign here: )
somewhere in the 3MB part (Miners can't charge this part)
S's sign for transaction ID 3 SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

Miners will only charge half the price of previous 2 transactions.

--- Does this really make miner lose? ---
NO
This Makes Miner pay same amount of electricity and same amount of processing power to process 4 times more transactions than before.
since they only mine block headers. (that 3MB part won't cost mining power.)
But they are not happy,
I don't know why I'm not a miner someone says they can't use ASCI mining on Segwit... or
may be they see the customer is increasing but profit is not increasing.

--- Miner's plan ---
NO Segwit!
but how!?
A Groups of Chinese miner Created there own Bitcoin(since bitcoin is open-source and easy to copy) which is Bitcoin-Cash and controled by them
And try to tell everybody Bitcoin-cash is the real bitcoin.

if you compare these two
The B-Cash is more centralized and pro miner compare to BTC
The BTC segwit is more decentralized and pro user. (you can use both old and new segwit way to transacte.) compare to BCH
(If you compare both to fiat both are decentralized.)
Segwit is 1-4MB in size
B-Cash is 8MB in size
Segwit is compatible with old nodes and recored in BTC BlockChain
B-Cash is incompatible and recored in BCH's BlockChain.

the following Im not sure.
-Segwit's structure change enables other application (the lighting network? easy for further upgrade?)
the following Im sure.
-B-Cash didn't change structure. just bigger size. that means when BCH user base grow up, it still will end up in Slow and high fees, for sure.

--- I hated those B-Cash promoters in Chinese website ---
The 1st time I saw B-Cash promoter is in a Chinese crypto forum named 8btc
They tried to demonize the BTC Core developer team in Chinese. to fool innocent Chinese people who have no English and Internet access to the truth.
the way they demonization is like Communism and cultural revolution to demonize U.S. and capitalism.
During that time I have no idea about what's going on, but I feel uneasy with these people and they out Number you.

--- BTC and BCH have conflict of interest. ---
Try to think BTC and BCH is 2 big computers
there processing power is from miners.
BUT!
They use same mining machines. If you put power on BTC, BCH loss power, and vice versa.

IF you are a miner. you paied 2000 USD for one machine to mine. you only have one!
Will you mine BTC or BCH? See!? they are conflict!

And most critical part is mining machines are mostly made by BCH people.

--- Why you should value decentralization on top ---
It enables you to do something that your country don't allows you to do.
Look at people in Venezuela and Zimbabwe. it's the 1st in time they can protect themselives from their country.
Look at people in China, it's the 1st in time normal people they can move their money freely out of China.

without decentralization it's not possible.

I'm not saying BTC is 100% decentralized. and BCH is 0% decentralized
It's relitive. BTC also centralized in some way but compare to BCH it's more decentralized.

--- What will happen when nobody mining BTC ---
let's say IF all the miners swich from BTC to BCH at same time.
BTC will halt!
no transaction will goes through.
and time goes by BTC will die.

--- The idea of killing BTC and BCH People will take over the world ---
--- I call it mining difficulty attack ----
--- it Used twice since 2017 luckly they are failed ---

1. Let BTC price goes high to attract newbis.
2. slow down BTC upgrade. don't upgrade BTC. Try to stop solve transaction throughput problem.
3. more Miners will mine BTC since price is increasing and BCH People is also mining BTC.
4. wait for BTC network difficultly adjustment to happen. (since there are too many miner join in, BTC network will raise the mining difficulty to Crazy high for next 2000 blocks, that required all miner on earth to full power there machine together to solve one problem in 10 minutes)
5. Since the BCH People also hold a large portion of BTC
6. BCH People sell large amount of BTC at high price for BCH and pump the BCH against BTC.
7. BCH People withdraw there mining power from BTC to BCH. (they control almost half of the mining power)
8. Step No.7 will make BTC network slow and BCH network fast
9. Use promoter on social network to tell people BCH is real bitcoin and BCH is fast and cheep.
10. Newbis will experience BTC is slow and expensive and BCH is fast and cheep.
11. other non-BCH people miner will also join and mine BCH since BTC's problem is crazy hard and BCH's problem is easy and fast.
12. BTC network slows down even more.
    ---- IF ----
    BCH price exceed BTC and BCH is more profitable and easy for miners.
    Miners will lose their reason to mine BTC and BTC network will be halt in history.
    except one reason
    ---- even maybe... IF ----
    There are small portion of miners that still believe in BTC will give them freedom
    They may run there machine full power to solve the next 2000 crazy hard bitcoin problems without profit
    (BTC price drop, miners got BTC reward for a very long time, and you still spend same amount of electricity.)
    These Miners won't able to make it financially (in this crazy hard 2000 blocks).
    and BTC network halt totally. Newbie's Panic sell.
    price drop to single digits.
    BTC will die.

--- How BCH to avoid the mining difficulty attack ---
BCH added a feature called emergency adjustment.
means if BCH network can't create a block for a long time the network will lower the difficulty without waiting for 2000 blocks.
that keeps the network running with less security.

--- OK... How to use segwit ---
In short, time is 2017 and it's not easy.
facts

1. No free wallets offer good segwit support.
2. Segwit comes with 2 types (address start with 3 and address start with bc1)
3. the adress start with 3 one is backward compatible (send and recevie with others) and the bc1 is not(other party need to upgrade and support).
4. I can't found one free good wallet give you address start with 3.
5. you have to risk youself to create your own BIP39 seed and input into one wallet support BIP49 like electrum.
6. as far as I know only expensive hardware wallet will give you address 3 segwit.

SO BUY HARDWARE Wallet now to use Segwit.
(Im not paid for saying this, I'm not a youtuber with xxxxx of followers, but this is the fact now)