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.
Media Player Classic and ZoomPlayer are capable of playing QuickTime files by using the QuickTime framework that gets installed by QT Lite. Windows Media Player and other DirectShow based players will require DirectShow filters to be able to play QuickTime files.
QT Lite contains exactly the same components as QuickTime Alternative. The ONLY difference between the two packs is that QT Lite does not contain Media Player Classic.