Transitions work by changing between a source and destination image over a specific, fixed time interval and can be employed almost anywhere, for instance, as a slides based screensaver, or perhaps as part of an audio reactive presentation. The more one works with Quartz Composer, the greater one's appreciation grows for its graphical facilities.
It is often the case that the transition is augemented by use of Image Filters.
See the example embedded below.
One cannot combine Image Filter protocol with any other protocol based composition although Graphic Transitions based compositions can combine any other protocol than Image Filter.