These are native MIME types for most browsers. Bitmaps are stored as a series of values, with each pixel taking a set amount of memory. Vector graphics contain a series of lines, curves and splines that form different shapes through mathematical instructions. Vector formats take the same amount of memory regardless of whether they are scaled big or small. Vector formats are resolution independent.
Vector graphics are more suited for line art, illustrations, type and flat-style artwork.
Bitmaps are better suited for continuous tone images, such as photographs, blurry images, soft edges, glows, and drop shadows. Since the standard web format is bitmap, most vector graphics have to be rasterized before they can be viewed. Flash is a vector format, both Freehand and Illustrator produce vector formats that can work in a Flash animation. GIF is a poor choice for most photographic images. GIF89a supports transparency, interlacing and animation.