You should also be aware that QuickTime .mov format is a container, not a codec. (Just like AVI is a container, not a codec.)
While QuickTime Player can play just about any .mov quickTime file, imovie cannot edit all QuickTime files.
.mov can contain many different codecs. For editing in iMovie, the most common is h.264, but many others will work, including DV, Apple Intermediate Codec, Apple Animation Codec, Motion JPEG A, etc.
You can tell which codec is used in a QuickTime file by opening the file in QuickTime Player. Then press Command - I to open the inspector. The video and audio codecs will be listed next to the workd "Format:"