Once upon a time, Rear projection CRT was a kind of television set, with a big CRT tube, which projects the picture onto the back of the screen - you might remember them. You might even have one! A modern rear projection TV can be as big as a CRT at the back (and indeed a lot bigger in general), but works on quite a different principle. Basically, the old CRT (cathode ray tube) television works by having a huge great glass tube in it, which "fires the TV signal" onto the front of the screen (no need to get any more technical than that!) The classic CRT tube is heavy, and rather breakable.
The modern rear projection TV has a completely different kind of screen (not glass), which lets the light that is projected onto its back surface through to the front. The picture is projected by... wait for it... a projector, similar to the LCD projectors you see used for business presentations and by people with very big walls in their living rooms (actually, it's a different technology called DLP, which uses some clever mirror-based technology)! The result is that rear projection TVs are just as biiig and bulky as the old CRT TVs, though nowhere near as heavy, and with less limitations on the size of the screen.
Check out a selection of rear projection (not CRT!) TVs on Amazon.com.
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