They are taken in addition to lecture and discussion sections. See pages 7-11 for details. The group leader will often explain the material that students find difficult, work additional examples, provide worksheets for additional practice,answer students' questions, assist with exam preparation, and coach the group through the course. No previous sign up is necessary.
Tutors are available to assist the groups as they work.
These are typically single reviews, but for Social Science courses, these take the form of pre-exam study groups consisting of at least two sessions.