What are lithospheric plates made of?

Lithospheric (or tectonic) plates occupy the ocean floor or land, and, depending on this, their structure changes. On land, they are considerably thicker and consist of three main layers: a basalt base, a granite middle layer, and a thin layer of sedimentary rocks at the top. And in the oceanic areas there are only two layers, basalt and sedimentary, due to which the bottom of the oceans is much lower than the land level. There are lithospheric plates that cover only the ocean floor or land area, sometimes they are mixed.