What I describes rock that were formed when molten rock cooled down?

Rocks that formed when molten rock cooled down are called igneous rocks. They can be classified into two main types: intrusive (or plutonic) rocks, which crystallize slowly beneath the Earth's surface, and extrusive (or volcanic) rocks, which solidify quickly at the surface. Common examples include granite for intrusive rocks and basalt for extrusive rocks. The cooling process allows minerals to crystallize, giving igneous rocks their distinctive textures and compositions.