PoW: Proof-of-work (PoW) is the mechanism that allows the decentralized Ethereum network to come to consensus, or agree on things like account balances and the order of transactions. This prevents users from "double spending" their coins and ensures that the Ethereum chain is tremendously difficult to attack or manipulate. As the underlying algorithm that sets the difficulty and rules for the work miners do. Mining is the "work" itself. It's the act of adding valid blocks to the chain. The more "work" done, the longer the chain, and the higher the block number, the more certain the network can be of the current state of things.