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 Digital camera
A portable camera that records images in a machine-readable format. These cameras eliminate the expensive and time-consuming methods normally involved in creating computer-readable images, including film processing and image scanning.