What is the difference between a lcd projector and a HDTV projector?

A LCD projector projects the image to a screen in front of it like a slide projector projects the images of slides onto a screen while a LCD tv projects from behind the screen like a large TV, the image coming to the screen from behind it rather from in front of it. That is basically the only difference. You can usually get a much larger image from a LCD projector than from a LCD tv. Projectors usually require more planning and installation events and you can not just pick it up and move it to another room easily.