Which earth layer does the following describe this layer along with the crust forms tye solid tectonic plates?

The layer described here is the lithosphere. The lithosphere is made up of the crust and upper mantle. It forms the solid part of the crust that is able to 'float' on the viscous lower mantle. The lower mantle, known as the asthenosphere, moves because of convection currenst and cause the rigid outer layer of the earth to move.