Answer:There are three main types of rocks: sedimentary, igneous, and metamorphic. Each of these rocks SIMILARITIES: formed by physical changes—such as melting, cooling, eroding, compacting, or deforming—that are part of the rock cycle.DIFFERENCES: Igneous rocks: formed from melted rock deep inside the Earth.Sedimentary rocks: formed from layers of sand, silt, dead plants, and animal skeletons. Metamorphic rocks: formed from other rocks that are changed by heat and pressure underground.