You know them by their logos: Lacoste, L.L. Bean., Abercrombie & Fitch. Popped collars and polo shirts are standard, and their grooming tends to be impeccable.
In your day, preps might have actually gone to prep school, but the category has grown since then. Today, they tend to be the latest incarnation of the in-crowd: the popular kids. Sometimes they overlap with jocks, especially when it comes to sports such as golf or tennis.
One of the things to watch for with preps is overachieving. Keeping up schoolwork, being involved in too many organizations or getting into the right college can stress them out. Maintaining the right image may even make them vulnerable to eating disorders.