Hundred of posts across the Internet are being passed back and fort debating the merits of Bimap over vector graphics. The bottom line is this. One of the most misunderstanding among casual designers is the different between bitmap (also known as raster graphics) and vector graphics. Here, I am telling you I am not going to explain what they are but I would rather link you to websites that explain the primary differences between these two graphics types and explain the area where usage of each most appropriate. I hope the following website will provide you with better understanding of the two graphics format
liz fulqhum has an introductory guide for client and designer to Vector and Bitmap graphics.
Mustex.com provides an informative on Vector and Bitmap graphic formats
About.com gives you a good explanation for the term Vector and Bitmap image files
