What is the "Markbook" tab of a textbook or the "Students markbook" of a group for?

What is the "Markbook" tab of a textbook or the "Students markbook" of a group for?

From the "Markbook" tab of a textbook or the "Students markbook" tab of a group, you can follow the progress of a student throughout a textbook or resource. The tab compiles the answers and results obtained in the activities that the student has completed autonomously (that is, without them having been assigned by the teacher).