In general usage, biceps usually refers to biceps brachii. The Biceps Brachii is attached to the forearm bone called the radius and originates at the scapula in two places. Biceps is a Latin term that means two heads (the Bicep gets it's name from these two heads - called the short head and the long head).

The Biceps runs down the anterior or front side of the humerus and makes up approximated 1/3 of the muscle mass of the upper arm

The biceps brachii are associated with strength. The size of the biceps can be increased through weight training.

The triceps brachii muscle is a large three-headed skeletal muscle. It runs along the back of the upper arm and serves to extend the forearm, hence it is an extensor muscle.

The three heads are called:

The Long Head
The Lateral Head
The Medial Head

The Triceps account for 2/3 of the arm's mass and people who exercise the arms with weights often neglect this group of muscles in favour of the biceps brachii.