Proof of Work
Proof of Work (PoW) has been the standard method where people could earn cryptocurrencies. Most famously associated with the Bitcoin network. For Proof of Work (PoW) miners secure the network by solving mathematical puzzles to confirm transactions to the network. And these miners then gets rewarded by their effort. This is how Bitcoin and many other coins works.
Today the difficulty of mining Bitcoin is extremely hard. And you need specialised mining rigs to be successful. In the beginning many people could mine Bitcoin using their personal computers at home.
There is a newer blockchain model known as Proof of Stake (PoS), that is different to PoW. Where you stake your cryptocurrencies instead of mining.