When lava cools and solidifies, it becomes igneous rock. Here's how it works:

* Magma: Molten rock *beneath* the Earth's surface is called magma.

* Lava: When magma erupts onto the Earth's surface, it's called lava.

* Igneous Rock: As lava cools and solidifies, it becomes igneous rock.

There are two main types of igneous rock, depending on how the lava cools:

* Extrusive igneous rocks: These form when lava cools quickly on the surface. They tend to be fine-grained because the crystals don't have much time to grow. Examples include basalt, rhyolite, and obsidian.

* Intrusive igneous rocks: These form when magma cools slowly underground. They tend to be coarse-grained because the crystals have more time to grow. Examples include granite, gabbro, and diorite.