You need braces if.....(1)

Your teeth are crowded, not in a straight alignment

The doctor would call this a CLASS 1 malocclusion

Your upper front teeth is too forward, over your lower front teeth. 

Your upper lip is protruder over your lower lip.

The doctor would call this a CLASS 2 malocclusion
OR Excessive overbite

Your upper front teeth is too far backward, over your lower teeth

Your upper lip is retruded over your lower lip

The doctor would call this a CLASS 3 malocclusion

OR underbite