In a proof-of-work (PoW) blockchain, transactions are bundled into blocks and added to the blockchain by miners. Miners compete to be the first to find a solution to a mathematical problem, and the winner gets to add the next block to the blockchain. The mathematical problem is designed to be difficult to solve, but easy to verify once a solution has been found. This process of finding a solution is known as "mining."
The proof-of-work system is used to create trust in the blockchain by ensuring that it is computationally infeasible for an attacker to tamper with the transaction history. An attacker would need to redo the proof-of-work for each block in the chain, which would require an enormous amount of computational power. This makes it very difficult to carry out attacks on a proof-of-work blockchain.
Proof-of-work is the most widely used consensus mechanism in blockchains, and it is used by many popular cryptocurrencies, such as Bitcoin and Ethereum.
