Proof of Authority (PoA) is a consensus protocol that gives only a few blockchain users the ability to validate data. PoA is not decentralized and is therefore less secure than other blockchains. However, Proof of Authority networks are more scalable, efficient, fast, and cheap than decentralized networks (e.g. Proof of Work, Proof of Stake). The centralized aspect of Proof of Authority systems may be preferred by some organizations and businesses.
Microsoft Azure is an example of a Proof of Authority blockchain.