#Blockchain is the new technology trend these days.Basically its a #Decentralized server.Which means that the user data is stored at more than one node but many.
As the name suggests the Blockchain has a blocks connected by the link called hashes.Every block has three parts
1)Data(The information stored in the block)
2)Hash of that block(address)
3)Hash of the previous block(address)

So the main advantage of blockchain system is
1)Enhanced Security
2)Transparency
3)Reduced cost and lower maintenance cost

1)ENHANCED SECURITY

Since the user data is not concentrated in one server it cannot be easily hacked.So lets take the example of the Decentralized voting app which is considered as the "hello world" program of the blockchain technology, even if you want to change a single vote you need to hack the whole system which might be spread across say some 50 servers called nodes.And the greatest advantage of the blockchain is that the data is stored in form of blocks whose information cannot be changed, if changed the hash value of the block changes.

2) TRANSPARENCY

The information stored in the blockchain is more transparent to the group of users.Bitcoin for example uses the concept called Proof of stake( #POS ) which means that at-least 51% of the node should accept the new piece of block to be added to the chain,Hence the data is checked and then added to the chain.

3) REDUCED COST AND MAINTENANCE

Since there is no centralized server there is no need of the costly servers and their maintenance cost reduces .You transfer the data to over the nodes which are active and constantly changing.You pay to the nodes which actually carried your system in crypt o-currency.