Life cycle means the stages a living thing goes through during its life.
In some cases the process is slow, and the changes are gradual. Humans have various stages of growth during their lives, such as zygote, embryo, child and adult. The change from a child to an adult is slow and continuous. In many societies it is marked by ceremonies at puberty.
In most insects the transition is sharp and well-defined: egg > larva > pupa > imago (adult).