RP is a way of pronouncing English in Britain. The letters stand for Received Pronunciation. Received here is an old use, meaning accepted as the proper form — not received a letter. For a long time schools, the BBC, and many highly educated people in the south of England treated this accent as the standard. It is the British accent many textbooks still teach, and the one you hear from an older kind of newsreader. Though actually, most people in Britain do not speak RP. Scotland, the north of England, London streets, and many young people sound quite different, and that is normal English too. RP is not better English; it became a social badge, a sign of class and schooling. Teachers may still use it as a clear model because the sounds have been described in great detail. Say the two letters: R-P.