Giovanni Arduino coined the term 'Quaternary' in 1759, after the discovery of Po Valley alluvial deposits in Italy. Later in 1829, it was used to describe the sedimentary rocks in the Seine Basin of France, by Jules Desnoyers. This period is mainly known for the glaciation activity and associated Ice Ages, punctuated by short interglacials. The period started with an Ice age in the northern hemisphere, and various ancestral species of flora and fauna dominated the landscape (like saber-toothed tigers and mammoths).
The Quaternary Period starts at the end of Neogene, and the boundary is marked by the Pliocene-Pleistocene Boundary Marine Extinction, which killed off a substantial number of marine organisms. Go through the timeline provided below to clearly understand the chronology of events in this period.
In the above image, it can be noted that the Quaternary Period is divided into two epochs, the larger one being Pleistocene, and the smaller one being Holocene. Pleistocene is further divided into four stages: Gelasian, Calabrian, Middle, and Upper. The Pleistocene Epoch started at around 2.5 Ma and ended at 0.01 Ma, after which Holocene epoch started and exists till present date.
Tectonics started shaping up the continents as they were more or less similar in today's appearance. Landmasses were becoming more and more recognizable. The glaciers started retreating quickly. The Skagerrak and Bosporus straits formed the present day Baltic Sea and Black Sea, respectively. This was the major consequence of sea level rise due to melting of glaciers and influx of freshwater into already existing former marine water bodies.
A land bridge formed between the European landmass and the Britain mainland, due to the cyclic rise and fall of the water level in the English Channel. A similar geological process occurred in case of the Bering Strait, and the continents of Asia and North America were also connected by a land bridge. Extensive flooding took place in the northwestern regions of North America. The Great Lakes and the Hudson Bay formed as the Canadian cratonic regions underwent extensive tectonic upheaval.
As this time is known for its periodic glaciations, the climate also changed accordingly from cold conditions to warm ones. But, the climate changed quickly enough to cause mass extinctions especially among the land fauna. Several species like the saber-toothed tiger, woolly mammoth, American cheetah, etc., became extinct at the end of Pleistocene.
Quaternary glaciations and the associated Ice Age can be said to be one of the most important identifiable characteristic this period, and evidences for the same have been preserved well all around the world. The glacial-interglacial cycles had a profound effect on the depositional environment of that time, when extensive erosion took place along with the formation of freshwater bodies. River and lake systems underwent some changes. The extensive ice sheets had an albedo effect (reflection of sunlight from a white surface), which lead to drastic drop in atmospheric temperatures. It is said that this event was caused due to the Milankovitch cycles, which explains the periodicity of solar intensity, which affects the Earth's climate.
Apart from hunting and discovering the use of fire, prehistoric man also evolved slowly and made different weapons and alternate ways of getting food, clothing, and shelter. He mostly expressed himself in the form of cave paintings, which are still remarkably preserved at some places on Earth.
A reason for this event includes the high possibility of a nearby supernova explosion, which might have greatly affected the thin ozone layer of the Earth's atmosphere, causing extensive climate changes. Ice started to melt from as far as the Great Lakes region, and this gave the opportunity to many other mammals to thrive. Humans extensively evolved around this time. Insects, angiosperms or flowering plants, and mammals started dominating on the planet.
The second mass extinction is said to started about fifty thousand year, and supposedly is still going on. The evidences are in the form of disappearance of numerous large animals such as the woolly mammoth. Also, the rapid evolution of humans caused the rise of civilization, and man began to hunt down fauna for meat and other livelihood reasons. In some cases, due to over-poaching, entire species of fauna became extinct shortly. This is said to be one of the main reasons of the ongoing extinction event.