Here's a bit more detail:

* Extrusive Igneous Rocks: These are formed when lava erupts onto the Earth's surface and cools quickly. They have a fine-grained texture because the crystals don't have much time to grow. Examples include basalt, rhyolite, and obsidian.

* Intrusive Igneous Rocks: These are formed when magma (molten rock beneath the Earth's surface) cools slowly underground. They have a coarse-grained texture because the crystals have more time to grow. Examples include granite, gabbro, and diorite.