Rhythm and Blues is a derivative of blues and pop from the 1940s mainly for a Black audience by Black artists. In its first years (and oftentimes since), it was used as a catch-all for Black music and a replacement of the term "race music".
Contemporary R&B typically follows the trends of modern pop and incorporates hip-hop more than blues. Pop is more similar to contemporary R&B than "classic" R&B is.
Joseph: Man I hate how people these days call Rihanna an R&B singer. Have they never heard Diana Ross?
Originally used to class music as "Rhythm And Blues", it has evolved to become a mix of different styles of music, such as hip hop, pop and crunk, over a (hopefully) wicked enjoyable beat. Quite easy to enjoy and dance to.
R & B can range from "Waterfalls" by TLC (often called 'old skool rnb) to "Golddigger" by Kyne West to pretty much anything from Outkast, etc.
R & B...Many people think its stupid I dont. It relaxes me, its something i can listen to without getting a headache or hearing to many "words". I love r&b, because its usually slow and many can relate to it in real life. It has a nice beat, and many types of music orginated from it.