Projector Contrast Ratio
Projector contrast ratio refers to the difference between the brightest white, and the darkest black.
The higher the ratio, the clearer, more complex images you will get.
If you see a projector with 1000:1 contrast ratio, this means that the brightest white is 1000x brighter than the darkest black. ( which isn't very high at all, aim for a higher contrast ratio )