The document discusses the three main types of rocks: igneous, sedimentary, and metamorphic. It describes how igneous rocks form from volcanic activity either inside the Earth as intrusive rocks or outside as extrusive rocks. Sedimentary rocks form from the compaction and cementation of sediments like sand and shale deposited over time. Metamorphic rocks are igneous or sedimentary rocks that have been altered by heat and pressure into a new form. The rock cycle shows how the different rock types are interrelated through geological processes.