The triceps brachii is a large muscle located at the back of the upper arm. It consists of three heads: the long head, lateral head, and medial head. This muscle is primarily responsible for extending the elbow joint, allowing for movements such as pushing and lifting. In addition to its role in elbow extension, the triceps brachii also assists in shoulder stabilization and extension. It is an important muscle for various physical activities, including sports and weightlifting, making it essential for overall arm strength and functionality.