Children need language to communicate with others. In the early years, language development is a way for babies and parents to communicate with each other. When the baby looks at a parent's face, the parent responds by cooing at the baby and smiling back. The baby learns to coo back at the parent, setting the stage for using language for social skills.
As children grow older and develop more of a vocabulary, they become capable of expressing their emotions through language. Using their words enables children to communicate feelings without acting out or throwing a tantrum to get the parent's attention.
Understanding the spoken word leads to a child's comprehension of right and wrong behavior and eventually moral development. When a toddler reaches for the oven and stops, repeating the parent's words "no" and "hot," he is internalizing rules communicated by adult authorities through language.
By the time a child reaches kindergarten age, he can absorb stories by listening and repeating them to others. He can also "read" books by using picture clues and by starting to recognize common words. Kindergartners recognize letters and begin to sound out words with the help of teachers and parents. They also begin to write letters and words at this stage of language development.
Eventually, a child can use language to convey information to parents and teachers. She can tell the person in charge when she is hungry or sleepy. She can relay her thoughts about things that happened during her school day that were important, such as, "Sarah brought in a caterpillar for Show and Tell today." She can tell a parent about a class assignment and when it is due, or if she is being bullied in school.
Eventually, children learn to appreciate artistic expression in the form of language such as stories, songs, plays and poetry. When they become familiar with the art form, they can begin to write their own poetry or predict how a story will end.