Mining in the cryptocurrency sense is covered in full under crypto mining, which explains how miners compete, what equipment they use and how the industry has developed. This page explains the word and how it is used across crypto.
On a proof-of-work blockchain such as Bitcoin, mining is the work of gathering pending transactions into a block and repeatedly hashing it until a result meets the network's difficulty target. The first miner to succeed adds the block and earns the block reward plus transaction fees. The name comes from an analogy with gold mining: effort and expense are spent to release a limited supply of something valuable, with new coins entering circulation gradually. Most miners now combine their power in a mining pool to earn steadier income, and large operators run warehouse-scale mining farms.
The word is also used more loosely. Proof-of-stake networks such as Ethereum after 2022 have no mining, but people sometimes still speak of "mining" when they mean staking or validating. Liquidity mining borrows the term for earning token rewards by depositing assets, with no computing work at all. Outside crypto, mining of course means extracting minerals from the earth, and "data mining" means searching large datasets for patterns.