The pectoral is a term relating to the chest. The "pectoralis major" is a large, fan-shaped muscle that covers much of the front upper chest. It begins at the breastbone (sternum) and the cartilage of the second to the sixth ribs and is attached to the collarbone (clavicle) to converge on the upper arm bone (humerus) just below the shoulder. Its main use is in moving the arm across the body. The "pectoralis minor" is a smaller, triangular muscle beneath the pectoralis major. It stems from the third to fifth ribs and converges at the shoulder blade (scapula), which it moves up and down.
The upper, or clavicular, portion of the pectoralis major raises the arm, while the lower, or sternocostal, is responsible for pulling the arm down.