The term 'chest muscle' refers to the muscles located in the chest area of the body. The most commonly known chest muscle is the pectoralis, which is a large, fan-shaped muscle that covers the chest wall and connects the shoulder to the sternum. It is also known as the 'pec' for short, and is composed of two parts: the pectoralis major and the pectoralis minor. The latissimus dorsi, or 'lat, ' is another chest muscle located on the back side of the body. It is a broad, flat muscle that connects the shoulder blade to the spine and helps with arm movement. Lastly, the term 'pecs' is often used to refer to the pectoralis muscles collectively.