In the early 1950s, the name rhythm and blues was derived from the style of popular black music at the time, which took the rhythm of rock 'n' roll music and incorporated it into traditional blues. Chuck Berry, Fats Domino and The Neville Brothers are all considered early rhythm and blues artists. Some also consider white artists such as Bill Haley and Elvis Presley to be early examples of what was then called rhythm and blues---although many of Elvis' biggest hits of the time were covers of songs originally by black artists. As more white artists began to appropriate the sound of rhythm and blues, it was more often than not just called rock 'n' roll music.
What constituted rhythm and blues changed in the 1960s, with the popularization of Motown and Memphis "soul" music, which became categorized as rhythm and blues. Popular artists of the time who defined this style included The Supremes, Otis Redding, Aretha Franklin and The Jackson 5. Soul music of the time performed by white artists was generally referred to as "blue-eyed soul" and was used to refer to artists such as The Righteous Brothers and Mitch Ryder.
Soul music splintered into subgenres in the late '60s and early '70s, and the definition of rhythm and blues changed again. Artists like James Brown took the soul template and made it more upbeat and dance-friendly, creating funk. Smooth soul, also called Philly Soul because many of the artists involved were from Philadelphia-based Stax Records, did the opposite and slowed soul down. Philly soul artists like The O'Jays and The Spinners were more reliant on vocals and complex musical arrangements that featured horn and string sections, creating a seductive sound tailor-made for romantic songs.
Soul music continued to be popular in the 1970s, as did disco music, which incorporated elements of funk and soul early on. As the decade progressed, rap music began to take hold, and it too incorporated elements of rhythm and blues in its sound, mostly by way of the samples used to establish beats. In the late '80s, rap and hip-hop influences found their way into rhythm and blues. Artists like Boys II Men, En Vogue and New Edition all took beats and production styles pioneered by hip-hop and put them into rhythm and blues, creating a popular subgenre called New Jack Swing that dominated rhythm and blues radio into the '90s.
As of 2010, rhythm and blues was a blanket term often used to describe any black artist who didn't predominantly use rap vocals in the music, although beat-centric rap production styles were frequently used. Rhythm and blues was more like pop music than ever before, and the two terms were almost interchangeable when describing massively successful artists such as Beyonce or Brandy. Often this type of pop/rhythm and blues was dubbed "urban" music. Just like rhythm and blues was in the 1940s, it was a term used to classify a style of music created by black artists, although white artists like Justin Timberlake were incorporating it into theirs as well.