Fire

Fire is the boldest of the six terrestrial magics. It’s wielded only by those it wishes to be wielded by. It is mischievous and destructive, but in its wake new life can take bloom. The world would be nothing without the flame, and the flame would be nothing without the world.
Mortal users of Fire are known as Pyretongues.

It's fire. That's literally it.
Ok, the fire CAN be different colours depending on the person but it really is just regular firebending.