What is bitcoin mining?
Miners are the engine that powers the blockchain. They check transactions are valid and then record them into blocks to be added to the chain.
There are two key questions that mining answers.
Bitcoin uses a peer-to-peer network, with no central authority issuing transactions. As a result, each node is likely to include different transactions in their respective blocks.
(1) How does the network decide which block to add to the chain?
Furthermore, computers are expensive to buy and operate.
(2) Why would anyone spend their resources running a node?