The College of Arms is the where you would come to have your family tree traced. Dating back to medieval times, when jousting tournaments were being organised, it was the chief function of the heralds to marshal and introduce the contestants and keep a tally of their score.
The knights were recognised by the arms they bore on their shields and the crests they wore on their helmets. Heralds soon acquired an expert knowledge of these and they were then recorded. The arms were then joined to the genealogy of the bearer as it stands today.
A continuation of class structure, you can arrange a special visit to research your arms if that takes your fancy. It's also the place where new arms are designed for important fellows such as Princess Diana.