Heraldry is the study of coats of arms: the pictures, colours, animals, and mottos that families, cities, and old orders put on shields, flags, and badges. In the Middle Ages a herald was the official who called out names, carried messages, and — though actually this became a huge part of the job — kept the records of who was allowed which picture, so two knights did not ride out with the same shield. Heraldry is the whole system around that work: the rules (which colours may sit on which, what a lion “means” in that picture-language) and the history of those family signs. You meet it in history class, in museums, and when someone talks about a school crest or a city’s coat of arms. It is a specialist, slightly old-world word; ordinary chat almost never needs it. People sometimes stretch it and call any fancy logo “heraldry,” though strictly a company logo is not a coat of arms and does not follow those old rules.