Screen resolution refers to the number of dots (or pixels) available for use on a computer screen. The most common screen size is 1024x768; there are many people who still use 640x480 and 800x600. In the future, more people will use larger screen sizes (like 1280x1024).
Keep in mind that many people (particularly older people) deliberately set their screen to show a lower resolution than the hardware allows, to make it easier to read.
Screen resolution is important is because it limits how much information you can show to your customer at one time. A usable website takes the varying screen resolutions of its customers into account.
to the glossary list)