The three different rock types are metamorphic, igneous and sedimentary. Metamorphic rock is made from rock that changed because of heat or pressure. Igneous rock is formed from magma that has cooled. Sedimentary rock is other materials like sand, mud and pebbles that get laid down in layers. The law of superposition says that the oldest rocks are laid on the bottom and the youngest are laid at the top. Scientists use rocks to learn how old the Earth is and also find fossils in them contributing to dating the Earth too.
The Triassic Period, from 252 million to 200 million years ago had the first reptiles and dinosaurs carrying on to the Jurassic Period. Eventually a mass extinction wiped them out.
The Cenozoic era is also known as the age of the mammals, flowers or insects. Life becomes more diverse, thrives and spreads throughout the world. "Early" humans also start to appear and grow into "modern" humans.