RTP stands for Run Time Package. In XP, VX, and Ace it was an additional download to get the resources such as music and art. Since it's been that way for so long it's come to mean "the resources that come with the program" to a lot of people here. This is no longer the way it works in MV but old habits die hard so you'll still see a lot of people calling it that even for MV. The rest of us are calling them default resources I think.