According to "The Encyclopedia of Human Development," the developmental stages of a child refer to the identifiable periods a child passes through on her way to adulthood. A stage includes biological, psychological and social growth. Though the stages are not constant across all children, the progression of stages is the same; each stage builds on the stage prior to it.
Sigmund Freud's theory consists of five stages. According to "Sigmund Freud" by Pamela Thurschwell, this theory supposes that children are strongly influenced by unconscious forces inside them and motivated by sexual and aggressive drives. According to his theory, each stage represents the child's focus on a certain aspect of the body. Until the age of 1, children are in the oral stage, where they focus on oral fixations such as sucking on the mother's breast. From 1 to 3, children are in the anal stage, where they focus on defecation. From 3 to 5, children are in the phallic stage, where they focus on the concept having or not having a penis. From 5 to 12, children are in the latency period, where the sex drive lies dormant. Lastly, from the age of 12 onward, children are in the genital stage, where the focus is on the child's genitals.
Jean Piaget's theory focuses on the cognitive development of the child. According to "The Cambridge Companion to Piaget," there are four stages in Piaget's theory. The child begins in the sensorimotor stage, which describes the learning of basic cognitive skills of an infant, and ends in the formal operational stage, where a child develops abstract reasoning skills. The complete set of stages are sensorimotor, from 0 to 2; preoperational, from 2 to 7; concrete operational, from 7 to 12; and formal operational, from 12 onward.
According to "Erik H. Erikson: Explorer of Identity and the Life Cycle" by Richard Stevens, Erikson's theory of development focuses on how a person's biology interacts with the environment through time. His theory contains eight stages, five of which take place during childhood. Each stage represents a particular struggle that a person will encounter at that period in her life. The stages are basic trust vs. basic mistrust (from 0 to 2), autonomy vs. shame and doubt (from 2 to 3), initiative vs. guilt (from 3 to 5), industry vs. inferiority (from 5 to 12), and identity vs. role confusion (from 12 to 18).