It is a subagent. It is called by the primary Agent (Opus in this case) to do some smaller task as to not waste the more expensive model (Opus) from doing a lower level task. I think the purpose is speed (parallel), maintain clear context, and to save money (simpler tasks can be done by a less expensive model).
From another thread:
More info here about subagents: https://cursor.com/docs/subagents