Igneous rocks are formed by the cooling of lava, which can either erupt from a volcano or cool within the Earth's crust. There are two main types of igneous textures: intrusive, where the cooling occurs slowly, resulting in larger crystals, and extrusive, where rapid cooling leads to smaller crystals. The texture of these rocks can provide insights into their formation process and the conditions under which they solidified. Common examples of igneous rocks include basalt and granite.