[BScout]

You can do a direct video out (this one may not be important to most people) (ie, hardware video online that outputs only the picture that can be fed to screens and projectors)

You can genlock the picture (if the playback video card supports it) so that the picture is in frame sync. This one is important to post-production and dialogue editors to keep absolute sync. The video offsets in Pro Tools are nowhere near as consistently accurate as actually have a playback video card and Pro Tools both on genlock/black burst sync (need Sync HD also for Pro Tools to do this)