Fire is a type of damage. It is usually direct damage.
Burning is another type of damage. This comes in the form of damage over time.
Lightning is like fire damage. It’s the direct damage that you probably see more often, but there are also abilities with electrocute damage, which is damage over time, like burning.
The Storm Totem and Wind Devil both apply electrocute damage over time. Flames of Ignaffar, and other Inquisitor spells also deal it.