The description and systematic classification of rocks, aided by the microscopic examination of thin sections.
The study of the origin, occurrence, structure and history of rocks, much broader process/study than petrography.
A branch of petrology dealing with the origin and formation of rocks. Involves a combination of mineralogical, chemical and field data.
Petrologic, petrographic, and petrogenetic studies can be applied to igneous, metamorphic or sedimentary rocks.
Petrology and petrography became important in geology in the mid 19th century with the development of the microscope and the thin section to aid in the description of various rock types.