what do you mean by complete and incomplete metamorphoses?

In complete metamorphosis, four stages occur in the life cycle of organism. These are egg, larva, pupa and adult. Butterfly undergo complete metamorphosis.
In incomplete metamorphosis, the pupa stage is absent, i.e. the insect completes its life cycle in three stages only. Cockroach, termites, grasshoppers etc. undergo incomplete metamorphosis.