A bitmap picture is made up of dots (pixels). The more dots, the better the quality (resolution). A bitmap will scale down in size OK. A bitmap will not scale up and retain the quality. Typical types of bitmap files are jpg gif bmp png tif psd. Read more about bitmap and vector graphics
A graphic image (picture) formed by a pattern of pixels. Also called a raster graphic.
A bitmap graphic is a pixel-based model for displaying images on computer screens. A bitmap graphic contains data about the color and coordinates of each pixel that needs to be triggered on the computer screen. Strictly speaking bitmap graphics ar not bitmaps, but pixelmaps. Bitmap graphic files are typically huge, so for better network transport they are compressed. The most typical bitmap compression methods on the Web are GIF, JPEG and PNG. Another method for displaying images on computer screens is vector graphics.