"Hurls molten rock over great distances. Sets the ground on fire, which really turns up the heat for enemy ground troops!"
The Lava Launcher is a very long range defense that hurls slabs of molten rock and sets that ground on fire!
Once the troops run over that area they will take damage for a certain length of time.
As you can see, the Lava Launcher range is massive! And what about the dead zone on the center? Huge! Basically you can only reach enemy troops outside the walls of your village, so always place it near the center.