Yes, it was back when the DAO got hacked and a lot of money was lost, it was decided by those in charge that they would role back the network to before the hack happened therefore acting as if the hack never happened, this rollback chain continued on as ETH so by rolling back they in effect forked Ethereum.

There were many opposed to this rollback as it defeats the point of the whole idea of crypto in having a central authority that can do what they want to, so we have ETC which is the original Ethereum chain untouched, so ETH is the fork and ETC is the original but because the big boys are in control of ETH this chain has the most attention and focus but for all purposes ETC is the original Ethereum.

It is getting a lot of attention now as there is an airdrop in early March, this is not a fork of ETC it is it's own blockchain based on the Ethereum protocol.