A seminar is a small group session which will probably happen once a week for each of your modules. Seminars support your lectures and allow you to explore the weeks topic in more depth. Content and format of seminars will vary from subject to subject, for example:
A seminar in English Literature will probably be a group discussion of a novel, poem or play
A seminar in Mathematics may involve trying to solve a mathematical problem as a group
A seminar in Education Studies could involve reading and critiquing a policy document or debating an educational issue
Some seminars may involve one student per week giving a presentation to the group, which could then be followed by a question and answer session or a discussion.