An alternative consensus mechanism that is less energy intensive than proof of work.

With proof of stake, there are no miners but instead validators. Validators must stake a certain amount of the network's cryptocurrency in a smart contract in order to validate transactions.

Validators are chosen based on a set order to validate the next block of transactions and be rewarded with newly issued cryptocurrencies from the network (also known as the 'block reward'). 

Validators who incorrectly validate a transaction or fail to keep their nodes online can lose all or part of their stake through a penalty called ‘Slashing’.