A Life Cycle describes the different stages an organism experiences as it goes through its lifetime. The stages and durations of life stages differ from specie to specie and may have many stages or just a few. An example of differing life stages can be seen in the life of a butterfly: starts as an egg, then the larval stage (caterpillar stage), the pupa stage (where it is inside the cocoon), and the adult stage (the butterfly who lays eggs, starting the cycle over again).
In psychology Erik Erikson developed a theory of human development involving differing stages of human development that cover the entire human lifespan (or life cycle). He discerned eight differing stages that humans experience. Each stage has a centralized conflict that is significant at the time and certain traits and behavioral outcomes are associated with different stages. The stages go from infancy (birth to 18 months) during which trust is established, to childhood (2-3 years) when toilet training happens, to the preschool stage (3-5 years), school age (6-11 years), and so on, all the way to maturity, which lasts from age 65 to death, when when people reflect on their life and try to have a sense of fulfillment.
Click here to learn more about Erik Erikson, including all the stages of the life cycle.