Ethereum Classic (ETC) is the original chain and Ethereum (ETH) is the new chain. The core developers, including the founder, went on and developed the new chain, and now when one talks about Ethereum they're referring to the new chain. Those that sticked to the original chain (ETC) -a small community- was ideologically opposed to any change imposed on the Blockchain, since they argued that it's nature should be immutable (not prone to change).Is there any real differences? In terms of functionality, both chains are the same since the originate from the same chain. It is more of a ideological difference. However it is important to take note that in terms of progress, the new chain would be more equipped with the latest updates and continual improvement of the system since the core developers are working on ETH, the new chain.