What is a phenomenon called in which the size of an animal isolated on an island increases dramatically?

Is there an explanation for why this might happen?

Lunarsea, There may be several as human cannot and don’t know everything about everything. Isn’t it exciting to have those thoughts and dreaming the wonder of the universe. ! ! !

shellawk, That’s just an assumption clearly it’s reasonable though. ! ! !

Lunarsea, It's because they have no natural prey. Like the Komodo dragon of Komodo Island.