Plasma screns, LCD monitors, Projection Screens, Interactive Whiteboards and Copyboards are measured diagonally across the screen. The diagonal is quoted in inches.
The display resolution is the number of pixels that can be displayed on the screen. It is often quoted in pixels or as an abbreviation of a standard e.g 640 x 480 pixels or VGA.
The most common resolutions are VGA - 640 x 480, SVGA - 800 x 600, XGA - 1024 x 768, SXGA - 1280 X 1024.