What is Proof of Work or PoW in blockchain?
Proof of Work (or PoW), in the crypto and blockchain context, is a consensus mechanism to verify transactions and secure the network. This is possible as each participant (known as miners) provides computational power to solve complex mathematical puzzles.
The first miner to solve the riddle is entitled to add the next block of transactions on the chain and is rewarded with newly created cryptocurrencies and transaction fees. The Bitcoin network is an example of PoW put into practice.
Unlike PoS or Proof of Stake, this validation protocol is less scalable and requires a lot of energy. Reasons that motivated the Ethereum Merge at the time.