Hi Ayesha !
Fragmentation - It is a process of reproduction in which certain multi-cellular organisms, on maturation, break up into smaller fragments, each of which develops into new individual. Example - Spirogyra. It occurs in invertebrates. It is more common in plants.
Regeneration - In this process, if an organism is split into several parts, most of the parts will develop into complete organisms. Example, Hydra and Planaria. It occurs in invertebrates as well as in vertebrates.It is more common in animals.