Upright Acoustic

whats the difference between an Acoustic Grand Piano and a Acoustic Upright Piano?

thanks
i notice the Grand are more expensive but whats the real difference?

An upright piano is one that general stands against a wall with a flat back:

http://pianoandsynth.com/wp-content/uploads/2008/02/yamaha_m460_acoustic_upright_piano.jpg

A grand piano has a full body so it’s much larger:

http://grandpianorental.com/images/C7.jpg

There are also baby grand pianos [...]