The Origin of Flags
Although evidence of flags used as symbols of tribal, national, and military identity can be found in ancient times, it wasn't until the Middle Ages that the use of flags becomes common, usually in the form of pennants or standards. Early European flags were largely religious in character, although the nobility developed a wide variety of standards with heraldic and genealogical emblems.
With the decline of feudalism near the end of the Middle Ages, the use of flags to represent nations began. Because suits of armor had been easily confused in combat, knights had to use shield designs and pennants to be recognized. The same problem had existed at sea. In fact, flags (called ensigns and jacks) were first used at sea because basically one gallon looks like any other gallon and a method of identifying whose ships were friendly and whose ships were not became important. As land battles began to involve larger and larger armies, and with the development of longer range weapons like cannon and artillery, combatants needed better methods of identifying friends and foes at a distance, and the naval ensigns evolved into flags and standards used on land.
In the United States, although flags were used in the colonies and during the revolution, they were still most commonly used at sea as naval ensigns or at military fortifications and bases. They were not commonly displayed by civilians and it wasn't until the Civil War that we began to see widespread use of national flags.
It wasn't until the 20th Century that the civilian traditions of displaying flags at post offices, schools, public places, and homes really become widespread.
Basic Flag Terminology
Banner - A piece of cloth attached to a staff used as a standard. It usually has a motto or emblem representing a person, organization, or cause as part of the design.
Canton - The rectangular or square area at the upper, inner quarter of a flag.
Colors - Another term used for a flag. This term is more commonly used to describe flags being displayed at ceremonies, parades, or by military color guards.
Emblem - A symbol used as an identifying mark, or an object functioning as a badge of authority.
Ensign - A flag flown as a symbol of nationality at sea, generally flown at the stern of vessels.
Field - The background surface of a flag.
Fly - The part of the flag furthest from the staff or pole.
Jack - Because sailing ships originally docked with their bows (front end) toward land the practice of flying a special identification flag called a jack at the bow when docked or at anchor became traditional. A jack usually looks like the union or canton of a national flag.
Half Mast - The practice of flying a flag from the midpoint of the pole as a sign of mourning; the custom in the United States is to hoist the flag to the top of the pole for a moment and then lower it to the halfstaff position.
Hoist - The edge of the flag beside (nearest) the staff or pole.
Obverse - The front of the flag when viewed with the hoist on the left.
Pennant - A long slender flag, usually tapered, triangular or forked. A flag used on ships for signaling or for identification.
Reverse - The back of the flag viewed with the hoist on the right side.
Standard - A banner carried at the top of a pole used to mark a rallying point. A flag, banner, or ensign, representing a nation or ruler.
Vexillology - [vek-suh-lol-uh-jee] The scholarly study of flags. The term was first coined in 1957 by the American scholar Whitney Smith. It is based on the Latin word "vexillum." The vexillum was a type of flag used by Roman legions suspended from a horizontal crossbar along its top side, which was attached to a pole.
Vexillologist - [vek-suh-lol-uh-gist] One who studies Vexillology, a flag historian.