Proof-of-stake (PoS) is a blockchain network consensus technique. The network's nodes pledge "stakes" of tokens for a predetermined length of time in return for a chance to produce the next block of transactions in PoS. The node that's chosen referred to as the validator will receive the block rewards in the form of the native token of the network.

💠 Working

Blockchain is a distributed ledger of transactions that is decentralised. Because the network is not controlled by a single server, there must be a way for everyone to agree on which transactions are valid. People could generate false transactions if this wasn't the case.Nodes are the servers that make up a blockchain. Transactions are processed by nodes. Some nodes have the ability to add transaction blocks to the chain, allowing the ledger to be maintained and expanded. These nodes are known as miners in Proof of Work (PoW) networks like Bitcoin. Instead of competing with each other to be rewarded for solving cryptographic puzzles as in PoW, nodes pledge payments to the network a process known as staking for a chance to be picked as the next block writer.

Source

Validators are individuals who are responsible for verifying transactions on a blockchain and are nodes that can add blocks in PoS networks. Each validator has a possibility to be chosen to write the next block and enjoy the incentives that come with it.It's kind of like a lottery the larger the stake of tokens committed the higher odds that node has of being chosen. The next block writer and validator are chosen in a pseudo-random procedure based on the size of the stake you as the user have invested in the network.