Artist roles are identifiers you can use to indicate to services what role a given artist played in the creation or performance of a given release. These roles can be indicated on the track level or the album level.
Stores accept the following artist roles from Boost Collective:
A main artist or "performer" is the major artist at the album level.
A primary artist is a main artist at the track level that is not a main artist at the album level. The primary artist role is used to indicate collaborations.
A featured artist is any artist assisting in the performance of a track but not at the fundamental level of a primary artist. Featured artists usually feature for a verse or as a vocalist on a song.
An artist that has remixed the original work.
The producer of the record. The role of a producer has become more diversified in recent years, but at this time, at least in Spotify, producer artist roles are listed under track credits.