Paxos in One Picture

 

If Accepted(N, quorum) happens, Prepared(N, quorum) always happens (right) before it. If Prepared(N, quorum) happens, it always happens before any Prepared(M, quorum) where N < M. If Accepted(N, quorum) happens, it always happens before any Prepared(M, quorum) where N < M.

Source: A Beginner's Guide to Paxos