Our planet earth is made up of natural solid aggregate of minerals or mineral matters, called rocks. They belong to three categories, the Igneous, Sedimentary, and Metamorphic. Igneous rocks are the first to be formed as primary rocks, while the metamorphic and sedimentary rocks are secondary in nature, as they are formed later through various geological processes under changed temperature and pressure conditions. When igneous rocks are formed by solidification of molten magma within the earth surface, are known as intrusive rocks, while when they are formed by the cooling of lava on the surface are known as extrusive igneous rocks. Igneous rocks are grouped as Phaneritic, Aphanitic, Porphyritic, Glassy or Vitreous, Pyroclastic, and Pegmatitic, depending upon their textures. Due to change in temperature and pressure conditions, rocks undergo metamorphic processes, called contact and regional metamorphism through several geological processes such as recrystallization, phase changes, Neo-Crystallization, pressure solution, and plastic deformation and, called metamorphic rocks. Based on grades of metamorphism, such rocks are called, very-low-grade, low-grade, and high-grade metamorphic rocks, while based on textures, they are identified as foliated and non-foliated rocks. These rocks are also grouped based on metamorphic facies, namely Zeolite, Prehnite-Pumpellyite, Greenschist, Amphibolite, Granulite, Blueschist, Eclogite, Albite-Epidote-Hornfels, Hornblende-Hornfels, Pyroxene-Hornfels, and Sanidinite facies. When igneous and metamorphic rocks are subjected to erosion, weathering, transportation, deposition, and compaction, they form sedimentary rocks, under terrestrial, coastal, marine depositional environments, and characterized by their colour, texture, nature of grains, mineralogy, and fossil contents. Structures such as beddings and ripples. are formed during their formation which are called primary structures, while the structures developed after the rock has been formed like stylolite, concretions, sedimentary dykes, deformations, etc., are called secondary structures. Stromatolite, Trace fossils, Coquina, Bioclasts, etc., are some of the organic structures found in such rocks. Sedimentary rocks are categorized as Clastic, Chemical, and Biochemical sedimentary rocks depending upon mode of formation and texture. Based on mineral composition, sedimentary rocks are identified as silicate or detrital rocks and non-silicate or Authigenic rocks. Nature of facies of these rocks, such as terrestrial, coastal, or marine, also helps in categorizing these rocks.