They are important because they help you decide how and what to play with your baby. Children will learn how to use their muscles. They will develop their skills of using their muscles at different rates. Some children will be quicker than others. Children learn to control their muscles in the same order no matter how quickly they learn.
Muscles develop from the head down to the feet and from the middle out to the fingers and toes.
First, infants gain control of their head muscles and then control their arms. The last muscles they learn to use are the leg muscles. Likewise, children learn how to control their neck and shoulders, then their arms before their hands and fingers. Keep your baby's hands free, rather than covered with mittens. Babies learn to use large muscles, like arms and legs, before they learn to use small muscles, like fingers and toes.