A barrette is a clip or pin that holds a small amount of hair away from your face. You might be especially fond of you butterfly-shaped barrette.
Barrettes are partly useful — they can keep hair out of your eyes — and partly ornamental. Young children sometimes wear brightly colored plastic barrettes in their hair, while adults tend to stick to more sedate, simple barrettes. The word barrette is a diminutive form of the French barre, "bar," after the size and shape of the typical barrette.