Mining refers to the process of validating transactions and adding them to the blockchain ledger. It involves solving complex cryptographic puzzles using computational power. Miners compete to solve these puzzles, and the first to do so gets the right to add a new block of transactions to the blockchain. As a reward for their efforts, miners receive a certain number of newly-created cryptocurrencies (like Bitcoin) and, in many cases, transaction fees.
Mining is critical for maintaining the security and integrity of a blockchain, as it ensures decentralization and prevents double-spending. However, it is also energy-intensive, especially in networks that use a Proof of Work (PoW) consensus mechanism.