Rock Types (I,S,M)
Although there are many different other kind of rock, all rocks can be grouped into three major families or types, depending on the way the rocks were formed. Those three families are the follow:

Igneous - The word "igneous" comes from the Latin word ignis, meaning "fire." Igneous rocks are formed by the cooling of hot, liquid rock, or magma. Over four-fifths of the Earth's crust is made up of igneous rock.

Sedimentary - Rock formed by the breaking down, deposition, and compaction of sediments. When bare rock is exposed on the Earth's surface, it is broken up into smaller pieces in many ways. These small fragments of rock are moved from one place to another.

Metamorphic - Rock formed below the Earth's surface when heat and pressure cause existing rocks to change their characteristics. Metamorphic rock is formed below the Earth's surface when rocks change their characteristics. This may happen in several ways.

If you want to know about the Rock Cycle click here!