Push-ups are a common bodyweight exercise that primarily targets the muscles in the chest, shoulders, and triceps. To perform a push-up, start in a plank position with your hands placed slightly wider than shoulder-width apart. Lower your body towards the ground by bending your elbows, then push back up to the starting position. This exercise can be modified to suit different fitness levels. Beginners may perform push-ups on their knees, while more advanced individuals can try variations like diamond push-ups or clap push-ups to increase difficulty. Regular practice can improve upper body strength and endurance.