Jivers is a term used to describe people who are passionate about swing dancing and jazz music. The term is derived from the word 'JIVE, ' which is a type of dance popularized in the 1930s and 1940s. CATS is an acronym for 'Cool And Tasteful Swingers, ' while HEPCATS is an acronym for 'Highly Experienced Professional Cool And Tasteful Swingers.' Both terms refer to people who are passionate about swing dancing and jazz music.