Short answers, pulled from the story.
Leather is a strong, flexible, and durable material made by tanning, or chemically treating, animal skins and hides to prevent decay. The manufacturing process divides into three core subprocesses: preparatory stages, tanning, and crusting, with an optional finishing step. Tanning stabilizes the hide's proteins, especially collagen, so the material resists heat, microbes, and decay.
Most leather comes from cattle, which supply about 65 percent of all leather produced, followed by sheep at roughly 13 percent, goats around 11 percent, and pigs near 10 percent. Other sources include horses for shell cordovan, lamb and deerskin, kangaroo, ostrich, and reptiles such as alligator, crocodile, and snake. Stingray and fish leather are also used for their durability.
Vegetable-tanned leather is the oldest known method, using tannins from plant matter such as tree bark, and it is supple, light brown, and not stable in water. Chrome-tanned leather uses chromium sulfate and other chromium salts, usually finishes in about a day, and is the most common modern method. Chrome-tanned leather is more supple and pliable and holds its shape in water better than vegetable-tanned leather.
Leather making has been practiced for more than 7,000 years. The leading producers of leather today are China and India, with India ranked as the world's third-largest producer and exporter of leather.
Leather production carries significant environmental impact from cattle rearing, tanning chemicals such as chromium, and air pollution including hydrogen sulfide and solvent vapors. One ton of hide can produce 20 to 80 cubic meters of waste water with high chromium and sulfide levels. The carbon footprint of bovine leather is estimated at 65 to 150 kg of CO2 equivalent per square meter.
Genuine leather does not describe a specific grade; in some countries it can mean nothing more than that a product contains leather. Leather grades include top-grain leather, which keeps the hide's outer grain layer, and within it full-grain leather, usually considered the highest quality. Other types include corrected grain, nubuck, split leather, bicast, patent, suede, and bonded leather.
Artificial leather alternatives include pleather, a portmanteau of plastic leather, made from polyurethane or vinyl coatings on a cloth backing, along with brand names like Naugahyde. Newer alternatives include cultured leather grown in a lab through cell-culture methods, mushroom-based materials, and a gelatin-based textile made from meat industry waste. Leather made from fungi or mushroom-based materials is completely biodegradable.