The document discusses three main types of rocks: igneous, metamorphic, and sedimentary. It provides details about the formation of each. Igneous rocks form from cooled magma and their color depends on the cooling rate. Metamorphic rocks form deep underground from the heat and pressure changing one rock into another. Sedimentary rocks like sandstone, limestone, and shale form from compressed sediments and contain visible layers. The document includes examples of each rock type and notes that the author collected mostly metamorphic rocks.