The term "bezel" comes from the jewelry industry, in which case a bezel is a groove that holds a gemstone or watch crystal in place. The term is also used to describe the rim around gauges, such as the speedometer in a car. In the computer industry, a bezel may refer to either the edge around a monitor or the front of a desktop computer case.
A monitor bezel, or screen bezel, is the area of a display that surrounds the screen. For example, if a monitor has a one inch bezel, the screen is surrounded by one inch of plastic or metal. If a monitor's bezel width is different on the sides than the top and bottom of the screen, the bezel specification will include individual measurements for each side. As displays have evolved, bezel widths have generally gotten smaller. For example, old CRT monitors often had bezel widths of two inches or more, while modern LCD displays often have bezels that are less than one inch thick. Thinner bezels help maximize the screen real estate of a laptops and make multiple desktop displays look more like a single screen when placed side by side.
A computer bezel is the front face of a system unit or "tower." Most PC bezels include have openings for one or more drive bays. These slots allow you to add devices such as an optical drive or an additional internal hard drive. When extra drives are not installed, these bays are usually covered by plates that are the same color as the bezel, but are not technically part of the bezel.