Short answers, pulled from the story.
Armour is a covering used to protect an object, individual, or vehicle from physical injury or damage, especially from direct contact weapons or projectiles during combat. It also protects against dangerous environments or activities such as cycling and construction sites. Personal armour protects soldiers and war animals, while vehicle armour is used on warships, armoured fighting vehicles, and some combat aircraft.
The word armour began to appear in the Middle Ages as a derivative of Old French and is dated from 1297, meaning a mail or defensive covering worn in combat. It comes from the Old French armure, which derives from the Latin armatura, meaning arms and equipment.
The first record of body armour in history was found on the Stele of Vultures in ancient Sumer, in what is now south Iraq. Scale mail also appears in surviving records from the New Kingdom of Egypt, Zhou dynasty China, and dynastic India.
In the early years of low velocity firearms, full suits of armour or breast plates could stop a bullet fired from a modest distance, so firearms stimulated the development of plate armour into its later stages rather than ending it. Full suits were worn by generals and princely commanders up to the second decade of the 18th century so they could survey the battlefield safely from distant musket fire.
During the 14th and 15th centuries armour seldom weighed more than 15 kilograms, but by the late 16th century it weighed 25 kilograms. The increasing weight and thickness gave substantial resistance, but required breeding larger cavalry horses to carry the load.
The US Army has adopted Interceptor body armour, which uses Enhanced Small Arms Protective Inserts, or ESAPIs, in the chest, sides, and back. Each plate is rated to stop three hits from a 7.62 by 51 NATO armour-piercing round at a range of 10 metres.
Armour for horses is called barding, especially when used by European knights, and body armour for war horses has been used since at least 2000 BC. Cloth, leather, and metal protected cavalry horses in ancient Egypt, Assyria, Persia, and Rome.