There are three types of Undergraduate Academic Representatives, each elected during the academic year by the cohort they represent:
Academic Affairs Officers (AAOs)
AAOs work on the Faculty level, and are committee members of the respective Faculty Unions. They manage the undergraduate Departmental Representatives in their Faculty. AAOs attend Faculty Teaching Committee and other Faculty-level meetings.
Departmental Representatives
Every department has at least one 'Dep Rep', who attends the staff-student committee for their department and manages their Year Reps.
Year Reps
Each year within each department has a Year Rep, who gathers feedback by speaking directly to their peers, and attends staff-student committees to pass on student comments about teaching quality and facilities.
You can download this Handbook as a PDF here,and the presentation from the training here.