Push-ups make the arms appear more sculpted and toned. This is because they are "the most effective way to build upper body strength," according to Best Health. They do not necessarily make muscles bigger, but they will tighten and firm the muscles on the arms and shoulder.
Push-ups build strength throughout the upper body, as they also benefit the chest and abdominals.
Growing stronger muscles does not necessarily mean implementing greater bulk; instead, building muscle constitutes "laying down lean and dense fibers that replace fat and boost metabolism" according to The Huffington Post. Bigger muscles come from exposing the fibers in the muscle to tension. When muscles experience tension, they signal to the body that they are enduring trauma, and the tears are repaired by the body.