What is a hotspot and where are they located?

Hotspots are thermal plumes within the Earth's mantle. They are located in various parts of the planet. The most famous is beneath the island of Hawaii. The chain of volcanic islands that make up the Hawaiian Islands were formed due to the drifting of the Pacific Plate over the hotspot. The big Island of Hawaii is currently over the hotspot and is the reason for the from Mt Kilauea.