Proof of Work is a type of consensus algorithm that is used to validate transactions on a blockchain. In Proof of Work, miners run powerful computers that have to work very hard to validate transactions in exchange for cryptocurrencies. Bitcoin uses Proof of Work to maintain it’s network, as do many other cryptocurrencies. While Proof of Work is a very secure way to maintain a blockchain, it is energy-intensive meaning that it consumes a lot of electricity. While this energy intensiveness is by design, many people cite it as a critique of Bitcoin and other cryptocurrencies.