What type of rock is formed from cooled molten lava?

Igneous rock is formed through the solidification and cooling of molten lava or magma. When lava erupts from a volcano, it cools rapidly when exposed to air or water, resulting in the formation of igneous rocks. These rocks can also form underground, where magma cools slowly, leading to different textures and mineral compositions.

This process is fundamental to the rock cycle, where igneous rocks may eventually be broken down into sediments, buried, and transformed into sedimentary rocks or subjected to heat and pressure, resulting in metamorphic rocks. In contrast, sedimentary rocks are formed from the accumulation of sediments, while metamorphic rocks are derived from existing rocks that have been altered by heat and pressure. The term "fossil rock" is not scientifically recognized as a distinct category, but rather, fossils are typically found within sedimentary rocks. Therefore, the formation process and definition of igneous rock directly relate to the cooling of molten lava, confirming that this is the correct answer.