Final answer:
Rocks are categorized as igneous, sedimentary, or metamorphic based on their formation processes. Formations are rock units with similar characteristics, and their study can reveal geological history and evidence of past life on Earth.
Step-by-step explanation:
The question pertains to the types of rocks and their formations. Igneous rocks form from cooled magma or lava, sedimentary rocks from weathered rock fragments or precipitated minerals, and metamorphic rocks from existing rocks altered by heat and pressure. Examples of these rock types include granite for igneous, sandstone for sedimentary, and quartzite for metamorphic. Formation refers to a rock unit with similar lithological characteristics, named after geographic locations where they were first described. The process of rock formation is ongoing and can lead to the creation of different rock types in the same area due to factors like tectonic activity. Sedimentary layers, such as banded iron formations, can also provide evidence of early Earth conditions based on their composition and layering.