Lithosphere
The lithosphere is the solid portion of the Earth. It is a dense shell of material that surrounds the entire planet. Even though most of the Earth's surface is covered with water, underneath that water is a solid layer of rock. With the exception of ice, basically any solid non-organic material you see on the Earth is from the lithosphere. This includes soil, rocks, sand, etc.

Composition
The most important thing to know about the lithosphere is what elements make it up. On page 11 of the Earth Science Reference Tables is a chart which provides you with all of the information you will need concerning the makeup of the different parts of the Earth.

The section under "crust" refers to the Earth's lithosphere. There are two different ways to express the composition. The chart shows which elements are most abundant by mass and by volume. As you can see, Oxygen is the most abundant element in the Earth's crust (lithosphere) by both mass and volume. Silicon is the second most abundant element by mass. Potassium is the second most abundant by volume.

All of the different amounts are right on the chart, so there is no need to memorize them. The most important thing to realize is that Oxygen is by far the most abundant element in the Earth's crust. Remember that this refers to Oxygen in compounds, not Oxygen as a gas! This Oxygen is present as part of solid chemical compounds in the rocks and soil.