Answer:
A hot spot is a volcanic region, far from the edges of the plate that might be heated up directly by the mantle underneath.
The Hawaii-Emperor Seamount chain is probably the most studied chain of volcanoes on the planet.
The bend on the chain is thought to be due to a sudden and radical shift of the Pacific plate in the past. Recent theories indicate it might also be due to movement of the hotspots due to activity under the mantle, rather than the movement of the whole plate.