Answer:
Moshi Monster codes are secret codes for a moshling. Some are easy to get but others are really picky so you'll need certain colours to get a certain moshling. It's best if you're a member because then you'll have a moshling zoo. You can have up to 6 moshlings in your room. You'll see all of them in your zoo and your room and others you'll see just in your zoo.
Good luck!