1. Intrusive igneous rocks: These rocks form when magma cools and crystallizes beneath the Earth's surface. They cool slowly, allowing for the formation of large crystals, resulting in a coarse-grained texture. Examples include granite and gabbro.

2. Extrusive igneous rocks: These rocks form when lava erupts onto the Earth's surface and cools rapidly. The rapid cooling leads to the formation of small crystals or even a glassy texture. Examples include basalt and rhyolite.