The biceps and the triceps are the main muscles in the upper arm, and most arm exercises use one or both of these muscles.
The biceps, as the name suggests has 2 heads. There is a long head on the outside part of the arm and a short head which is on the inside part of the arm. Both parts of the biceps start on the shoulder blade, and they run down to the bones of the forearm.
The main actions of the biceps are to bend the elbow and supinate (turn the palms up) the forearm. Any time you bend your elbow you will work this muscle, but it will work the most efficiently when your palms are faced up. 3 of the most common bicep exercises are dumbbell curls, barbell curls, and the bicep machine. All of these exercises are great for both men and women.
In addition to isolation exercises for the biceps, you can also do back exercises and work your biceps at the same time. Exercises like pull ups, seated rows, or the lat pull down will work both your back muscles and your biceps at the same time.
The triceps are on the back of the upper arm, and as the name suggest has 3 heads-long, lateral, and medial. The long head starts on the outside of the shoulder blade. The lateral head starts on the outside of the back of the humerus, and the medial head starts on the inside back part of the humerus. All three portions of the triceps, attach to the elbow.
The main action of the triceps is to straighten the elbow, but the long head will also help to pull the shoulder backwards. The triceps work in exercises like push ups and dips, and you can also use dumbbells, barbells, resistance bands, or machines to work your triceps.
If you want to build big arms, perform multiple sets with heavier weights, but if you just want to tone your arms choose lighter weights and perform fewer exercises for your arms.