Brightspace uses different icons to represent the type of activity that is associated with a grade item in the grade book:
A question mark displayed next to a grade in the grade book means that grade is associated with a quiz.

A question mark appears to the left of a learner’s quiz score in the gradebook.
By clicking the question mark icon, you will be able to see the submission for that item, including the completion summary, grades, and attempt(s) of the learner. A pop-up window will appear, where you can choose to view the attempt either by the general completion or view the details by attempt number. If you would like, you can set your quiz to automatically add learners’ quiz grades to the grade book.

View a general summary of the learner submission under “Completion Summary”, or view the details by specifying the attempt number in the drop-down menu at the top.