The department or function of a convention which registers members. Members are either pre-registered or at-the-door.
Pre-registered members pick up their badges (often produced in advance) and convention publications and (sometimes) freebies. Pre-reg members are often asked for identification.
At-the-door members pay for their memberships, get badges made on the spot and get the same convention publications and freebies as advance members.
The Registration department is usually also responsible for providing program participants with materials supplied by the program department and, after the con producing a list of members.