What is difference amongst different image file formats?

Question

What is the difference between JPEG, PNG, BMP, ICO, GIF files?

Which go with what applications? Any one superior in picture quality, resolution? Any diffrence in size?

I've noticed BMPs are used mostly in wallpapers. JPEGs for pictures. When do you use one over the other?

Answer 1

In summary, jpeg offers great compression so filesize is smaller compared to BMP and it can support millions of colours. BMP has no compression and most application including windows wallpaper can now support JPEG instead of just BMP back in Windows 3.x. GIF format supports only I think 256 colors but it can support animated gif.

Answer 2

Quality and Capacity.