Imagine you're watching a football game on TV and someone in your family asks who's winning. The "Packers," you reply.
But maybe this family member doesn't know much about football. They look at the screen, complaining that they can't tell who is who. So you simplify it. "The ones in green are winning," you say.
Well, heraldry is basically the same idea. It developed in 12th century Europe as a way of distinguishing between "teams" on the battlefield.
Back then, battles between warring nobles or kings were fought by knights who were completely covered in plate armor. They wouldn't know whom to attack except for the "coats of arms" or "arms" painted on shields and woven into cloaks and banners.
These "arms" were combinations of designs and symbols that came to signify certain individuals, families, and military and political units.
The emblems could be quite ornate, but most depicted a shield with crowns, animals, a motto and other symbols on and around it.
But there's a lot more to heraldry than simply being a fancy identification card.
The word heraldry actually refers to the use and regulation of the distinguishing emblems. The coats of arms are the emblems themselves.
Heraldry wasn't always used just for military purposes. As methods of warfare changed, the need for identifying marks diminished. But heraldry continued to grow. Lots of people couldn't read or write, but they could recognize emblems. So nobles transferred their coat of arms to a seal and stamped documents and letters. And since arms were used exclusively by noblemen and rulers, they became a sign of social status.
Heraldry was a carefully guarded system. Only the nobility could have coats of arms, and you couldn't duplicate another family's emblem.
"Heralds" regulated the system. Originally messengers between rulers and the people, heralds became arms' record-keepers. They kept track of who had what design, prevented people from claiming false ancestry (and thus, a coat of arms), and helped devise new designs.