QuickTime is Apple's own proprietory video format and QuickTime player is the official player for it. Nowadays however, it can handle much more than the standard QuickTime MOV format and it can play just about anything if you install Perian to complement it.
Note that this particular version only works on Snow Leopard i.e. OS X 10.6.3+. QuickTime X has superseded it but it does not support older formats. QuickTime Player 7 supports older media formats, such as QTVR, interactive QuickTime movies, and MIDI files on Snow Leopard and OS X Lion. It also accepts QuickTime 7 Pro registration codes, which turn on QuickTime Pro functions.
As you would expect from an Apple product, Quicktime is extremely slick to use to the point of sometimes "hiding" features that you would expect to be more readily available - such as creating playlists for example. When it comes to performing basic functions such as playback, it's very easy to use although launching it is still a little slow.
If you want to really get the most out of QuickTime 7 however, you need to upgrade to the Pro version which allows you to do much more such as edit and convert video files. QuickTime 7 is designed to play Apple's MOV video format although as mentioned earlier, it can play much more than this with Perian installed. However, there are other players such as VLC media player which do this without third party plugins and are much quicker to launch.
Quicktime is by no means essential nowadays but it still remains Apple's flagship media player and is definitely worth upgrading to the Pro version.
- Improves security and is recommended for all Mac OS X Leopard users.