There is a huge amount of crypto currencies in the world, but it all started with Bitcoin. Bitcoin was the first crypto currency, all other crypto currencies are just alternative currencies. And that's where the term "Altcoins" comes from, alternative coins. This means all crypto currencies except Bitcoin itself.
No matter if the currency is already known like Ethereum or completely unknown, it is always an Altcoin. It also does not matter whether the currency has a block chain or a completely new technology behind it. Every crypto currency, except Bitcoin, is automatically an Altcoin.
