The queue of assignments waiting to be marked.
Quizzes do not appear here
Quizzes are marked automatically, on the server. What is in this queue is assignments — answers a person has to read.
So if a quiz is not here, do not wait for it; it has already been marked.
Marking can unlock the next lesson
If a lesson is gated on completing an assignment, the student stays behind it until a mark is recorded.
Which means the grading queue is not only paperwork; people may be waiting on it.
Feedback is separate from the mark
You can give both a mark and written feedback. What you write is shown to the student — this is not an internal note.