The solid Earth has three primary subdivisions that are defined by differences in composition. These are the crust, the mantle and the core. Although these terms are known by most literate people, the discussion that follows will necessarily present some additional names that will be unfamiliar to many. However, I have attempted to keep the scientific jargon to a minimum - think of it as learning the names of the organs and processes within a body different from your own. In addition, many of the concepts and terminology are not universally agreed upon, especially so because we are in a time of rapidly evolving understanding of Earth's interior.
Lithosphere is a term that has been used in a variety of ways by different authors.
I will use it to refer to the part of the Earth that behaves in an elastic manner, i.e. when deformed it will return to its original shape after the stress is removed, as will a rubber band. For example, 10.000 years after the continental ice sheet melted, the lithosphere of the Canadian shield is still rebounding from the weight of the glacier that weighed it down for 100,000 years. The lithosphere includes the crust and the uppermost part of the mantle. An important thing to remember is that there is very little actual molten rock within the crust and mantle, otherwise S waves could not pass through. The oceanic crust is largely made up of submarine basalt flows that were extruded along mid-ocean ridges, shallowly emplaced igneous intrusives and a relatively thin overlying layer of sediments.