there are three, softfork, hardfork and fork a coin. softfork and hardfork has been explain above.

fork a coin means you clone a coin and create a new coin with new genesis and blockchain. you need at least 2 nodes in order to make your new coin/blockchain live.

there are list of coins that has been fork from for example bitcoin, bytecoin, monero and others. you can refer to this website https://mapofcoins.com/ and https://forkmaps.com