Lava is molten rock that originated from the mantle of a planet. Usually extracted through volcanos either on land or underneath water. Not to be confused with magma, which is molten rock that is still under the planets surface. Magma turns into lava after it erupts onto the surface. The core of Earth is often confused to be magma or rock, but most scientists believe it is iron or some other metal creating the magnetic poles.
Lava fields are very dangerous; if you step in it you will lose your foot.