Assignment group owns a queue of work. Assigned to identifies the person handling a task. A record can have a group and no individual owner while it waits for triage. Confirm the person belongs to an appropriate team before assigning them; a name in a reference field alone doesn't prove capacity or responsibility.
Use Active to distinguish working queues from records that are resolved, closed, or canceled. Filtering by an empty assignee without Active can include canceled work. A task record contains common fields shared by specialized task types, while an incident adds incident-specific fields. Notifications can inform an assignee about a change, but a notification doesn't substitute for setting the ownership fields. The saved record is the operational source of truth.