Immensely popular from about 1989-1992, it's a style of R&B that focuses on a very prominent swingbeat made with an electronic drum machine. Vocals are usually harmonized.
Other modern R&B releases are tagged with Contemporary R&B. Either this or New Jack Swing are now preferred by Discogs to the less precise RnB/Swing. The earlier blues-soul bridge genre is tagged as Rhythm & Blues.
New Jack Swing evolved in the late '80s, when urban contemporary soul artists began incorporating hip-hop rhythms, samples, and production techniques into their sound. Some songs simply had hip-hop beats, others had rapped sections and sung choruses.