The type of rock formed from cooling and solidification of molten material is called igneous rock. This process occurs when magma beneath the Earth's surface cools to form intrusive igneous rocks like granite, or when lava erupts and cools rapidly, forming extrusive igneous rocks like basalt. The characteristics of igneous rocks, such as texture and mineral composition, depend on the cooling rate and the environment of formation. These rocks are significant in geology, providing insights into volcanic activity and the formation of the Earth's crust.