SplitMovies is an application that specializes in splitting a single movie file into multiple independent video clips, each of which is a stand-alone movie clip and can be opened and played back. Currently, SplitMovies supports the following movie formats for imports: AVI, Matroska (MKV), QuickTime. If you import a QuickTime-readable video clip, SplitMovies will split it into multiple MOV clips.
So why do we want to split a movie file into multiple independent clips as opposed to parts? Simply, you can't play back file parts with a media player like Apple's QuickTime Player and VLC Media Player. Furthermore, if you lose just one part, the original movie can no longer be recovered. On the other hand, if you use SplitMovies to split a movie file into multiple clips, each of them becomes an independent video file. So you can play them back individually. If you lose one of them, you cannot combine them into the original movie file. But the damage is minimal because the rest of the clips are still viewable.
* Please note that SplitMovies may not work with media clips that are protected by DRM.