2. What is it?

The QuickTime Browser program is a utility to catalogue your 
QuickTime movies. A collection of movies can be made into a 
Library, but are not internally stored (just the location of the 
movie is stored). This means that large collections can be made
but the library remains small - around 10k for about 80 movies.
Movies can be viewed quickly by clicking on its name in the list. 
Movies that have been created in several different applications 
can be put into a single library for easy browsing.