Votes
Voting is done by +1 / -1, and is either majority, or allows -1 to serve as a veto (with an explanation) only in very specific cases. Votes are required for releases to show the explicit approval of a sufficient number of PMC members that the software release is appropriate.
Many projects use votes rarely, and instead work by consensus. That is, committers proposing new work will take the time to get general consensus from the rest of the project, and will proceed with new work unless someone states an objection that has a clear rationale, and alternate plan forward.