Assistant Director (1st, 2nd, 3rd, 2nd 2nd)
Internet Filmmakers' FAQ
Aka 1st AD. The person who organises the crew to the best advantage for filming. They say things like "quiet please" and "turn over". They will act as floor manager or stage manager and efficiently draw together the necessary elements for shooting. The 1st AD usually designs and controls the shooting schedule and generally liaise between the production office and the set. Contray to popular belief, working as a 1st AD is generally not a stepping stone to directing – most ADs go on to become production managers and producers.
Aka 2nd AD. Under the supervision of the 1st AD, the 2nd looks after the cast. They also occasionally take charge of the set and organise the next day's call sheet. 2nd ADs tend also to be a liaison between the set and production office.
Aka 3rd AD. Usually the assistant to the 1st AD, but can also be charge with responsibility for looking after the extras on a film.
2nd 2nd Assistant
Same as a 3rd AD - it just depends which school of terminology you graduated from.