CLAM is a POS (Proof-Of-Stake) coin that has been around since the CLAM Project launched around early May 2014.

The coins were distributed to every Bitcoin, Litecoin, and Dogecoin address that had a non-dust balance early May of 2014. The addresses that qualify each contain 4.60545574 CLAM each. The developers believed that this was the most optimal way to initially distribute and get the coin into as many hands as possible.

If you have a wallet.dat file that had either BTC, LTC, or DOGE on May 12, 2014, chances are you may be sitting on CLAM coins that just need to be extracted through a process called "digging". You can dig for clams by downloading the client, syncing it, and importing a BTC, LTC, or DOGE wallet and scan for any addresses that may be funded. There are a couple of 3rd party services that can "dig" for you as well. Also keep in mind you need both the public and private keys of the wallet.dat to claim the coin.

So far, only 222,840 of 3,208,032 sets of 4.60545574 CLAM have been dug up so far from the initial distribution.

CLAM is a proof-of-stake coin that provides ongoing distributions, approximately 1 CLAM/minute is given away for wallets that support the CLAM network by staking.

An easy way to think of the ongoing distributions is by comparing it to a raffle ticket drawing where a prize is awarded. 1 CLAM = 1 raffle ticket, so the more CLAM one owns and stakes, the more likely one would be awarded the ongoing 1 CLAM distribution for supporting the network.

It's popular with a well-known crypto game site, but I've also personally used them as a means of payment or receipt for goods and services.

Anyway, this is just a bird's eye view of CLAM coin. Hope I didn't confuse, but let me know if I need to clarify or expand on something!