A torch is a handheld light. Although flashlights are sometimes called "torches," technically a torch has a burning flame.
Torch can also be used as a verb indicating that something has been purposely set on fire. For example, arsonists have been known to torch empty buildings just for fun. This meaning dates to 1931. The noun form of torch has been around a lot longer. In the late 13th century torch came into English from the Old French word torche, or "twisted thing," which was a piece of wax-dipped rope.