Why there are more sources repos on my raspbian wheezy?
For what are they needed?
Collabora has improved software for the foundation under contract. They implemented Hardware acceleration inside Webkit (for Ephiphany) and did work on a Wayland desktop called Maynard.
It makes sense that they run an extra repository with the improved versions.
As the directory would suggest, those are the list of "sources" from which
apt-get will pull applications from.
etc/apt/sources.list.d/raspi.list lists the official repos, and
/etc/apt/sources.list.d/collabora.list appears to be an official mirror.
In addition to the individual files in the
/etc/apt/sources.list.d/*.list files that Jacobm001 refers to, the "master" file in
/etc/apt/sources.list is also used - it pre-dates the "individual repository file in a sub-directory" format that Debian (and thus Raspbian) now uses, and will probably have at least a reference to a
mirrordirector.raspbian.org source which actually redirects requests to a local mirror for you.