What Raster graphics is
Also known as "bitmapped graphics" these programs store images in the form of patterns of screen pixels. Unlike "draw programs" (vector graphics), these "paint programs" can create detailed patterns of shading that convey an artistic touch, but any attempt to rescale or resize the image may result in unacceptable distortion. Raster-based graphics have become a standard technology and are popularly known by their GIF and JPG formats. Raster graphics use pixel-by-pixel definitions as opposed to vector graphics which use computer algorithms to describe shapes, lines, animation, etc.
The meaning of Web designer
The aesthetic and navigational architect of a Web site, the designer is the person responsible for how the site looks and feels. He or she is the one who takes the heat if the graphics are fuzzy, the links are too light, or something is hard to find on a Web page. Usually this person is trained in the creative side of image development; however, an extensive knowledge of Web-based programming and information architecture is considered fundamental to being a successful Web designer. (That and good client-relationship skills are a must.)