Short answers, pulled from the story.
Jerry Wexler of Billboard magazine is credited with coining the term "rhythm and blues" as a musical term in the United States in 1948, though the phrase had appeared in Billboard as early as 1943. Before that, Billboard's tracking of black popular music ran under the heading Harlem Hit Parade, created in 1942.
Rhythm and blues replaced the term "race music", which had been coined by Okeh producer Ralph Peer based on how the African American press described itself. Some record companies had already begun replacing "race music" with the term "sepia series" before "rhythm and blues" became the standard.
Commercial R&B bands of the 1950s through 1970s typically consisted of piano, one or two guitars, bass, drums, and saxophone. Arrangements were rehearsed to the point of effortlessness and were sometimes accompanied by background vocalists.
New Orleans producer Dave Bartholomew first introduced the Cuban tresillo rhythm into R&B on his 1949 disc "Country Boy", using it as a saxophone-section riff layered over a swing rhythm. Professor Longhair similarly blended Afro-Cuban rhythms with blues, and his style was known locally as rumba-boogie. The Bo Diddley beat of 1955 is considered the first true fusion of 3-2 clave and R&B/rock and roll.
Rhythm and blues originated in African American communities in the 1940s, drawing from jazz, blues, gospel, and boogie. The Rock and Roll Hall of Fame identifies Louis Jordan's Tympany Five, Joe Turner's big band, James Brown, and LaVern Baker among the originators, with Jordan and Turner credited with laying the foundation in the 1940s.
In the late 1980s a newer style called contemporary R&B developed, combining rhythm and blues with elements of jazz, soul, funk, disco, and electronic music. New jack swing artists like Teddy Riley and Keith Sweat gained hits, while artists such as Usher, TLC, Aaliyah, and Mary J. Blige found success in the category. In 2004-80% of songs topping the R&B charts also reached the top of the Hot 100.