Here's why:

* Intrusive refers to the fact that the magma (molten rock) intrudes into existing rock layers beneath the surface.

* Extrusive igneous rocks, on the other hand, form when lava erupts onto the surface.

Some common examples of intrusive igneous rocks include:

* Granite: A light-colored, coarse-grained rock often used in construction.

* Gabbro: A dark-colored, coarse-grained rock.

* Diorite: An intermediate-colored, coarse-grained rock.

Intrusive rocks cool slowly underground, allowing large crystals to form, giving them a coarse-grained texture.