Igneous rocks are one of the three main types of rocks, along with sedimentary and metamorphic rocks. They are formed through the cooling and solidification of magma or lava. Magma can be derived from partial melts of the Earths mantle or crust, while lava is molten rock that has been erupted onto the Earths surface. Igneous rocks occur in a wide range of geological settings, including shields, platforms, orogens, basins, large igneous provinces, extended crust, and oceanic crust.

There are two categories of igneous rocks: intrusive and extrusive. Intrusive igneous rocks, also known as plutonic rocks, form when magma is trapped deep inside the Earth and cools slowly, resulting in coarse-grained rocks. Extrusive igneous rocks, also known as volcanic rocks, form when lava cools rapidly on the Earths surface, resulting in fine-grained or glassy rocks.

Igneous rocks are geologically significant because they make up 90-95% of the top 16 kilometers of the Earths crust by volume. They also form about 15% of the Earths current land surface, and most of the Earths oceanic crust is made of igneous rock. Igneous rocks are important for understanding the Earths history and geology, as well as for their economic value as sources of minerals and building materials.