|Mining is a part of coming to a consensus on a blockchain that uses the Proof-of-Work method to agree on the order of events.|
A miner is somebody that looks at what is happening on the network and records every transfer of money. Two different miners might have a different opinion about the order in which some transactions happened. Every miner writes everything they saw happening on the network in a block. Now there are many miners on a blockchain, and therefore many different opinions.
All the miners have to find the answer to a problem, that only powerful computers can solve. The miner that solves the problem first gets to add their block to the blockchain. The winning miner’s opinion will become the truth accepted by everybody else on the network.