Rhythm and blues
Rhythm and blues (abbreviated as R'n'B or R&B) is a mixed genre of popular music which initially was performed by African American musicians. It has absorbed such combinations as blues together with jazz and gospel. The term was introduced in 1949 by the people who created music charts of the American magazine Billboard instead of the dismissive expression 'race music' that was in wide usage earlier. With the weakening of race segregation in USA the term 'thythm and blues' developed into a broader meaning and began to denote also soul and funk music played by musicians of all races and nationalities. It's not common to include rock music, hip-hop or reggae in this term as these genres developed as separate music genres some time later.
It should be noted that there is a distinct difference between what is called rhythm and blues today and the classic rhythm and blues. The modern R'n'B means a musical genre which is based on a symbiosis of blues, soul and other 'race' genres. And the classic rhythm and blues is considered to be the music on a pronounced blues basis. Many people consider the classic rhythm and blues music to be a part of rock music, and the notion of "rhythm and blues" they understand as modern R&B. This is a very common misunderstanding. Many critics still argue whether the notion should mean a genre of rock music and whether the term itself should have its "more common" meaning. According to some of them this would be easier, and thus it is right. The others think that only the pecularities of the music should be the basis for classification.