canvas-lms/doc/examples/group_assignment.md

The following diagram provides an example to describe the structure of group assignments. It also shows the correspondence between the fields of an assignment override API request and the resources they map to.

The components in yellow are group sets. When creating or updating an assignment override, you will refer to the group set by the group_category_id field.

The components in green are groups. An assignment can become a group assignment iff it has a group_category_id that maps to an active group set, as well as a group_id that maps to an active, valid group. In the API, you will be specifying the group by the group_id field of the assignment_override construct.

Important: an assignment must be assigned to a group set (the group_category_id field) on creation for an override with a group_id to be effective.