The layer of the Earth composed mostly of silicate rocks is known as the crust. The Earth's crust is divided into two categories: continental crust and oceanic crust. The crust is the outermost layer of the Earth, varying in thickness, with continental crust being thicker and primarily composed of lighter elements, while oceanic crust is thinner and denser. Understanding the composition and structure of the crust is vital for geology, natural resource exploration, and understanding plate tectonics.