Projection TVs form a small image on a device inside the projector - either a CRT or LCD - and then shine that image onto a screen is located within the TV box itself. In a rear-projection TV, light reflects off the projection display panel and is then projected onto the screen.
Typically referred to as "big-screen" TVs, these large-cabinet TVs generally have built-in screens measuring at least 40". Up until a few years ago, all rear-projection TVs used three CRTs to create images. Using CRTs resulted in cabinets that were relatively heavy and bulky — nearly always designed as floorstanding TVs. Newer digital microdisplay rear-projection technologies, like DLP, LCD, and LCoS, make possible the more compact, lightweight "tabletop" big-screen TVs.