In this world of cryptocurrencies you have probably already heard of the word altcoin, but what is an altcoin?
Long story short an altcoin are all the coins that aren't bitcoin such as ethereum, XRP, dogecoin, cardano, litecoin, EOS, stellar, monero, tezos., etc...
Almost all of the altcoins come from the bitcoin source-code.
Different altcoins have different purposes in the real world.