Igneous rocks formed within the crust are called

Igneous rocks that form within the Earth's crust are called plutonic rocks. These rocks form when magma cools and solidifies slowly beneath the Earth's surface. Because of the slow cooling process, plutonic rocks typically have large, visible crystals. A common example of a plutonic rock is granite.

To better understand, imagine that magma is like a molten rock mixture. When it finds its way into the Earth's crust and cools down very slowly, it gives enough time for the crystals to grow large. This is different from volcanic rocks, which are formed when magma reaches the surface, cools quickly and forms smaller crystals.