Salsa, in the musical sense, is a contemporary musical style, which draws influences from a number of other types of music and cultures. It is often described as Afro-Cuban from the influence of those cultures on the rhythms that are prevelant. It was also an outgrowth of the earlier Mambo scene in this country.
Salsa, in the dance sense, is a simply a dance that expresses the rhythms found in Salsa music. It too, has roots in Mambo and other latin dances such as Cumbia and Charanga. Many of the steps in Salsa can be extended to those dances.