Dips are the parallel-bar exercise that works the triceps and chest.
A standard dip begins with the exerciser supporting their body on parallel bars, arms straight and shoulders above the hands. They lower the body by bending the elbows, then press back up. The triceps extend the elbows, while the pectoral muscles and anterior deltoids assist. A closer grip generally emphasizes the triceps; a wider grip and forward lean place more emphasis on the chest.
Dips are a bodyweight movement, but they can be scaled in either direction. Resistance bands or an assisted dip machine reduce the effective load for beginners. Stronger athletes can add weight with a dip belt, vest, or dumbbell. Ring dips use unstable gymnastic rings and demand more shoulder and trunk control than fixed-bar versions.
A muscle-up is not simply another name for a dip. It combines a pulling phase that gets the athlete above a bar or rings with a transition into a pressing dip. Bench dips are another variation, performed with the hands on a bench and the feet supported elsewhere; they reduce the amount of body weight being lifted and differ biomechanically from parallel-bar dips.