The Project Management Committee (PMC) is the group of people with formal oversight of the project.
Committers are peoples with write access to the source code repository. All PMC members are implicitly committers.
Contributors are peoples who contributed to the project through emails, patches, merge requests, mentoring or other means.
Emeritus members are peoples who are no longer active (for example because they no longer have time to work on the project) but are still entitled to many of the rights and privileges of the position. Emeritus status indicates interest but not activity, as opposed to having resigned.