The Earth's crust is the outermost solid layer of the planet. It's the part we live on and what we see when we look around.

Here's a more detailed explanation:

* Location: It's directly above the Earth's mantle, which is a semi-solid layer.

* Thickness: The crust is relatively thin compared to the other layers, ranging from about 3-5 miles (5-8 km) thick under the oceans (oceanic crust) to about 25 miles (40 km) thick under the continents (continental crust).

* Composition: The crust is primarily made up of igneous, sedimentary, and metamorphic rocks.

It's important to note that the Earth's crust isn't a continuous shell. Instead, it's broken up into large pieces called tectonic plates. These plates are constantly moving, interacting with each other, and causing earthquakes, volcanoes, and mountain formation.