Which best describes igneous rock?

Igneous rock is best described as including intrusive and extrusive rock categories because these terms help to differentiate how igneous rocks are formed based on their cooling locations. Intrusive igneous rocks, also known as plutonic rocks, crystallize slowly below the Earth's surface from magma, leading to larger crystals. Extrusive igneous rocks, or volcanic rocks, form when magma erupts onto the surface as lava and cools quickly, resulting in smaller crystals or a glassy texture. This distinction is fundamental to understanding the characteristics and formation processes of igneous rocks.

The other options do not accurately describe igneous rock. The first option mixes igneous, metamorphic, and sedimentary rock categories, which is unrelated to the specific characteristics of igneous rock alone. The second option incorrectly limits the formation of igneous rock solely to above-ground lava, neglecting the significant role of magma in the Earth's crust. The fourth option refers to minerals formed from erosion, which relates more to sedimentary rocks rather than the formation processes and characteristics of igneous rocks.