The viola is the "medium" of the string family. It looks almost identical to the violin, but it is a little bigger. The viola is famous for its dark, chocolaty sound. It also has 4 strings and is held under your chin on your left side, even if you're right handed!
Anyone of any size or shape can play the viola!
Check out this website for cool information about violas:
http://www.playmusic.org/string/index.html