A descarga is an improvised jam session consisting of variations on Cuban music themes, primarily son montuno, but also guajira, bolero, guaracha and rumba. The genre is strongly influenced by jazz and it was developed in Havana during the 1950s. Important figures in the emergence of the genre were Cachao, Julio Gutiérrez, Bebo Valdés, Peruchín and Niño Rivera in Cuba, and Tito Puente, Machito and Mario Bauzá in New York. Originally, descargas were promoted by record companies such as Panart, Maype and Gema under the label Cuban jam sessions. From the 1960s, the descarga format was usually adapted by large salsa ensembles, most notably the Fania All-Stars.

A jam session is a relatively informal musical event, process, or activity where musicians, typically instrumentalists, play improvised solos and vamp over tunes, drones, songs, and chord progressions. To "jam" is to improvise music without extensive preparation or predefined arrangements, except for when the group is playing well-known jazz standards or covers of existing popular songs. Original jam sessions, also called "free flow sessions," are often used by musicians to develop new material (music) and find suitable arrangements. Both styles can be used simply as a social gathering and communal practice session. Jam sessions may be based upon existing songs or forms, may be loosely based on an agreed chord progression or chart suggested by one participant, or may be wholly improvisational. Jam sessions can range from very loose gatherings of amateurs to evenings where a jam session coordinator or host acts as a "gatekeeper" so that appropriate-level performers take the stage to sophisticated improvised recording sessions by professionals which are intended to be broadcast live on radio or TV or edited and released to the public.