Final answer:
Igneous rocks form by solidifying from molten rock, either magma or lava. There are two main types of igneous rocks: extrusive igneous rocks and intrusive igneous rocks. Extrusive igneous rocks cool quickly on the Earth's surface and have fine grains, while intrusive igneous rocks cool slowly beneath the Earth's surface and have coarse grains.
Step-by-step explanation:
Igneous rocks are rocks that form by solidifying from molten rock, either magma or lava. There are two main types of igneous rocks: extrusive igneous rocks, which form when lava cools quickly on the Earth's surface, and intrusive igneous rocks, which form when magma cools slowly beneath the Earth's surface. Extrusive igneous rocks have fine grains and look dull, while intrusive igneous rocks have coarse grains and can sparkle due to the larger crystals.