Pull-down, Pull-up   

When film is transferred to video, in addition to some discrepancy between film frame and video frame/field (see 2-3 pulldown: film to video transfer) there is a subtle speed shift between the two media.
Since frame per frame, film runs 1.001 the speed of video some adjustment needs to be made if the sound is being synced to video but ultimately will be used as a film track. 

This discrepancy is corrected by changing the speed of the audio track (pull-up: speeding it up). 

 Many post production systems (Deck, ProTools, DA88 8 track recorder, etc.)  have facilities for this though usually it is handled at the post production lab stage.
Transfer situation: Suggested action:
Film transferred to video (or non-linear editor) for editing. Audio recorded on location with film is also transferred to non-linear editor or DAW synced to time code.  Long takes with sync dialogue may run out of sync: The image on the editor will be a tad slower than the audio.  This generally won't be a problem with short takes. Pulling-down the audio for these long takes will insure exact synchronization during editing.  If final product is going to be a film then any audio pulled down will need to be pulled-up before transfer to film stock.
As above, audio will be used on film (optical) track. Audio should be pulled-up.  It has been synchronized to a slightly slower copy of the film. To now be in sync with the actual film stock the audio tracks need to be sped up slightly.  This may be done after the mix as most mixes are done to video.
As above, audio will be used for video only release. No change required.