The most common type of rock is igneous rock, formed from the solidification and cooling of molten rock, or magma. Igneous rocks can be categorized into two main types: intrusive (or plutonic), which cool slowly beneath the Earth's surface, resulting in coarse-grained textures, and extrusive (or volcanic), which cool rapidly on the surface and typically have fine-grained textures. Common examples of igneous rocks include granite, which is intrusive, and basalt, which is extrusive. These rocks are foundational to the Earth's crust and play a vital role in the rock cycle, influencing geological formations and landscapes.