What is a validator?

A term similar to Bitcoin miners, a blockchain validator is someone who is responsible for verifying transactions on a blockchain. Once these transactions have been verified or ‘validated’, they are then added along with the new block to the chain. 

In proof of work (PoW) systems used in blockchains like Bitcoin, miners compete to solve increasingly complex mathematical problems to win the right to verify transactions and earn a reward. In proof of stake (PoS) systems, validators are chosen at random based on how much of the network’s token e.g. ‘Ether’ they stake to have the opportunity to validate new blocks of transactions and add them to the blockchain.