Answer:
The two subcategories of igneous rocks are intrusive and extrusive igneous rocks.
Step-by-step explanation:
The igneous rocks are the rocks that form from cooling magma and lava. They are the base for the formation of the two other types of rocks. The igneous rocks are divided into two subcategories, intrusive and extrusive.
The intrusive igneous rocks are the ones that form from magma that didn't manage to come out on the surface but gradually cooled off into the crust. The extrusive igneous rocks are the ones that have formed from lava that cooled off and that has come out on the surface or very close to the surface.
Because the extrusive and intrusive rocks take different times to form because of the difference in temperature and pressure on the surface and deep into the crust, they have differences in their appearance. The most noticeable difference is that the intrusive igneous rocks have coarse grains, thus large and well-defined ones, while the extrusive ones have fine grains, thus very small and almost unnoticeable.