Block Reward

When a block is found the miner is awarded a pre-determined amount of the coin, - called the coinbase transaction.

This is the primary mechanism miners earn money and often the only mechanism to mint new coins into proof-of-work blockchains. At pre-determined intervals the amount of coins awarded in the block reward decreases by half - known as a halvening.
With a predictable amount of coins being created at predictable intervals, the inflation of coins is known, predictable, and un-cheatable.

Eventually - around the year 2140 - , the Block Reward becomes almost non existent. When this happens miners will rely on other mechanisms for profit, which may come from transaction fees, business sponsorship, altruism, investment, idealism, etc etc.