Over the years, a number of different bitmap image formats have been developed. Each has it's own unique characteristics which determine when and where you might choose it over the others. However, whatever format you choose, there are programs that will convert it to any of the other formats. All of the still images that you see on the Web, or in multimedia programs, and many that you see in print, have been created or manipulated on a computer in a digital format. The kind you use determines the tools you choose.
Bitmap formats are the ones used for digital photographs.
Vector formats are used only for line drawings. Bitmap images are defined by their dimension in pixels as well as by the number of colors they represent. For example, a 640X480 image contains 640 pixels and 480 pixels in horizontal and vertical direction respectively. If you enlarge a small area of a bit-mapped image, you can clearly see the pixels that are used to create it. When viewed normally, the small pixels merge into continuous tones much as the dots used to create newspaper photographs do.