What is the difference between proof of work, proof of action, and proof of authority?

Proof-of-work (PoW) is a consensus algorithm where nodes on a blockchain network provide evidence they have used computational power to achieve agreement about transactions. 

Proof-of-action (PoA) utilizes nodes to facilitate operation of an algorithmic protocol to identify contributions in the external world blockchain, such as contributing money to a reclamation project or participating in an IZE digital property, and to correspondingly determine how IZE reward is distributed among node operators through the Elevate Blockchain in recognition of such contributions.

Proof-of-authority is another consensus algorithm where a limited number of trusted validator nodes validate the transactions. These trusted node owners are usually known entities with their reputations on the line for the right to validate blocks.