A central idea of blockchain technology is the distributed ledger. It is called a distributed ledger because instead of being stored in a central location, it is stored across a network of computers all around the world. For a distributed ledger to work, the entire network collectively has to agree with the contents of the ledger; this is the job of the consensus mechanism. The most popular blockchain consensus mechanisms are the Proof of Work (PoW) and Proof of Stake (PoS) systems., A number of other systems exist, such as Delegated Proof of Stake (DPoS) and Federated Byzantine Agreement (FBA) however this article will be focussed on presenting and then comparing PoW vs PoS.
more:
https://medium.com/@poolofstake/how-to-crypto-part-iii-proof-of-work-and-proof-of-stake-664dd2368ad0