An Earl or Jarl was an Anglo-Saxon and Scandinavian title, meaning "chieftain" and it referred especially to chieftains set to rule a territory in a king's stead. In Scandinavia, it got out of use in the Middle Ages, whereas, in Britain, it became synonymous with the continental count.
Today, an earl is a member of the British peerage, and is below a Marquess, but above a Viscount. A British Earl is the same as a continental Count. Since there is no feminine form of Earl, the wife of an Earl has the rank of Countess (the continental equivalent).