PoA is the acronym for Proof-of-Authority.
Proof-of-Authority is an experimental consensus algorithm used in distributed cryptocurrency networks. Generally speaking, PoA networks are based on a delegated scheme whereby a trusted/vetted group of nodes process, pack, and publish transactions. Nodes wishing to participate in network consensus must still stake crypto assets, just as in a PoS environment. The novelty of a Proof-of-Authority implementation is rooted in the mechanisms concept of staking IDENTITY/REPUTATION. Participants are disincentivized from acting maliciously by risking not only their assets/investments, but also their reputation.