A countess is a woman of the same high rank as an earl (in Britain) or a count (in much of Europe). She may hold the title herself, which is rarer, or she may be the wife of that man — and in Britain, the wife of an earl is called a countess, because English has no everyday word 'earless'. It is a title word, a little storybook, a little news-about-palaces. You would not use it for a rich woman with no title. Though actually students often hear count and think of numbers; this count is the nobleman, a different word that only looks the same. Older books love countesses; young people mostly meet them in films and history class.