Igneous rocks are made from lava or magma. Lava and magma are made of hot, melted minerals. Lava is found on or near the Earth's surface. Magma is found far beneath the Earth's surface.

Extrusive igneous rocks are made from lava that cooled quickly. Extrusive rocks generally have either no crystals or very tiny crystals. Intrusive igneous rocks are made from slow-cooling magma. Intrusive rocks have large crystals.

Extrusive Igneous Rocks: pumice, basalt, obsidian, scoria, rhyolite, andesite
Intrusive Igneous Rocks: granite, gabbro, diorite

On Earth's surface, wind, ice, and water can break rock into pieces. They can also carry rock pieces to another place. Usually, the rock pieces, called sediments, drop from the wind or water to make a layer. The layer can be buried under other layers of sediments. Sometimes, the sediments can even be made from seashells and bodies of plants and animals. Fossils are found in sedimentary rocks. After a long time the sediments can be cemented together to make sedimentary rock. In this way, igneous rock can become sedimentary rock.

Detrital sedimentary rocks are made from broken pieces of other rocks.
Chemical sedimentary rocks
Organic sedimentary rocks are made from the bodies of dead animals or plants.

Detrital Sedimentary Rocks: sandstone, shale, siltstone, conglomerate, coal
Chemical Sedimentary Rocks: chemical limestone, halite
Organic Sedimentary Rocks: fossil-rich limestone, coquina, coal

Metamorphic rocks are made from older rocks, either igneous or sedimentary. These rocks are changed by great heat and/or pressure deep beneath the earth's surface. The heat and pressure makes crystals in the rock. If the rock already has crystals, the heat makes the crystals larger. Sometimes the pressure flattens the crystals into layers.

With great heat and pressure, these rocks change to:

Foliated metamorphic rocks have layers or bands of crystals. (slate, gneiss)
Nonfoliated metamorphic rocks do not have layers or bands of crystals. (marble, quartzite)