ethereum is a token to be used for smart contracts.
there are lots of other technical differences too. such as the supply, mining, block time, block size, ... what is is exactly you are looking for?
other coins are altcions which do a wide range of different things. some are tokens like ETH, some try to be currencies. but there are a lot of differences between them in technology, usage, advantages and disadvantages.
Your Avatar remind me of that mini-drama, just imagine those sitting in that room had listen to that advise some of them will be in huge profit by now. Bitcoin is just starting