I recently sent out 25 invitation for one of those "home parties." I sent the invitations two weeks prior to the event with a "Please, Please RSVP!" To date I have only received one response out of the 25 invitations sent out. I'm starting to think that most people don't know what RSVP means.
With the holidays nearing and many people having parties, this may refresh the minds of many the proper etiquette for responding to invitations.
In the context of social invitations RSVP or Rsvp is a request for a response from the invited person. It is an initialism derived from the French phrase repondez s'il vous plaît, meaning "Please respond."
The high society of England adopted French etiquette in the late 18th century, and the writings of Emily Post aim to offer a standard no more stringent than that tradition. Late 20th century editions building on her 1920s beginning work say, e.g., that "Anyone receiving an invitation with an R.S.V.P. on it is obliged to reply....", and some recent editions describe breaching this standard as "inexcusably rude".
Emily Post advises anyone receiving an invitation with an R.S.V.P. on it must reply promptly, and should reply within a day or two of receiving the invitation.
While an RSVP request expects responses from both those attending and not attending - I think there is confusion that many people misunderstand the concept and do not respond if they are not attending.
The phrase "RSVP, regrets only", or simply "Regrets only" is a popular modern variation on the Emily Post RSVP, with the effect (if most of the invitations are accepted) of reducing the communication effort by both host and guests. The host thereby indicates intent to treat lack of a response offering regrets (e.g., "I regret I cannot attend ....") as indicating intention to be present at the event, and obviates response by attendees.
I hope this is helpful to those sending out invitations and to those who need to RSVP.