Ether Classic (ETC) is a cryptocurrency that was created due to a disagreement with the way original Ethereum network conducted business.
The catalyst for the split was due to a hacker finding a way to steal $60m worth of Ether coins. The supporters of ETH said that the code should be altered and the stolen coins should be refunded, while the supporters of ETC said that “code is law” and whatever happened happened – even if it was not ethical.
So in real life what happened is that ETC was the same original Ethereum Network code and ETH forked their code to create a new Ethereum Network.
Therefore two identical competing currencies were created that had two different exchange rates. Today ETH’s priced around 10 times higher and is more common around the general cryptocurrency community, though the basic concept is the same.