Resolution is the number of pixels as measured from left to right and top to bottom of your image. Currently SVGA (800x600) and XGA (1024x768) are the most common projector resolutions. An XGA projector has about twice the number of pixels of an SVGA projector, but it will also cost a bit more.
We recommend a XGA, or a high resolution native widescreen formats like WXGA, as the best choice for HDTV, DVDs and other home theater applications.
There is more to image quality than just resolution. Brightness uniformity and the kind of screen you are projecting on are also key players in image quality.