QT Lite is a trimmed down version of QuickTime that contains only the essential components needed for playing QuickTime content that is embedded in webpages.
Advantages of QT Lite are:
Quick and easy install Ability to make an unattended installation No background processes No unwanted stuff and other nonsense Smaller size
Media Player Classic and ZoomPlayer are capable of playing QuickTime files by using the QuickTime framework that gets installed by QT Lite. Other players will require DirectShow filters to be able to play QuickTime files.
If you want to play QuickTime files in Windows Media Player or another DirectShow based player, then it is recommended to install the K-Lite Codec Pack. That contains all the DirectShow filters that are required to play QuickTime files.