Here's a breakdown:

* Igneous comes from the Latin word "ignis", meaning "fire".

* These rocks are formed when molten rock (magma or lava) cools and solidifies.

There are two main types of igneous rocks based on how they cool:

* Extrusive rocks: These form when lava cools and solidifies on the Earth's surface. Examples include basalt and obsidian.

* Intrusive rocks: These form when magma cools and solidifies beneath the Earth's surface. Examples include granite and diorite.