An infant is a child from birth to one year old who needs significant care. The document outlines motor and language development milestones in two stages of infancy: 0-5 months and 6-12 months. In the first stage, infants can grasp objects, roll over, and babble or coo to communicate. In the second stage, infants can watch and hold objects, crawl, sit independently, take steps, say recognizable words, and understand familiar words.