You can give each of your friends a friend badge to show them what kind of friend they are in your eyes.
You give these badges to friends on your Friends page.
You can give each friend one badge, and you can have as many friends with the same badge as you like.
The friend page is also where you can see what badges your friends have given YOU.
Once you give a model a friend badge, the greetings you'll get from them will be flavoured to match their badge type. So if you give a friend the Sporty badge, they might make "the wave" for you :)