The primary goal of motorcycle helmet is to protect the rider's head during impact, although many helmets provide additional conveniences such as face shields, ear protection etc.

The conventional motorcycle helmet has 2 principal protective components:

a)	Thin, hard outer shell made of a thermoplastic or fibre glass (sometimes Kevlar or carbon).
b)	Soft thick protective padding made of expanded polystyrene or expanded polypropylene foam.
The purpose of hard outer shell is:
a)	To prevent penetration of the helmet by a pointed object that might otherwise puncture the shell.
b)	To provide structure to the inner liner so it does not disintegrate upon abrasive contact with the pavement.
The purpose of the protective padding is:
a)	To crush during impact, thereby increasing the distance and period of time over which the helmet stops.
b)	Reducing Deacceleration.