"What does R.S.V.P. stand for?" I asked the question when I was young and have been asked it many times since then. R.S.V.P. stands for the French phrase: Répondez s’il vou plaît. It means: please respond. However, it's not that simple; there are several ways to respond to an invitation. Some invitations do not include the request to R.S.V.P., but it is still courteous to inform your host or hostess of whether or not you plan to attend. Invitations that do have R.S.V.P. may include a response card. This is typical for formal invitations such as wedding invitations. Fill out the card as directed and mail as soon as possible. Keep in mind that as soon as possible means the next day or two!
If the R.S.V.P. is given with a phone number or e-mail address, respond likewise. Remember when calling, that it is best not to leave a message as you will never be sure that it was received. An invitation that does not include a specified means for replying should be responded to by a written note. The note should be sent, like the response card, within the next few days. So, next time someone is puzzled by R.S.V.P. you will know: "It is French and it stands for Répondez s’il vou plaît, which means, 'please respond.'"