It is an incredibly break-neck speed dance, and is known dancing to the beat of the music.
LA (Los Angeles) Salsa, as opposed to the New York Salsa, is danced 'On 1'. The tempo is normally medium to fast, and the dancers use this to their advantage as they demonstrate complex footwork and intricate body movements. Hard Salsa, more formally known as Salsa Dura, highlights strong musicality and a heavy use of percussion.
Dancing with the beat is what New York On 2 Salsa is all about, and as such, there is a very specific type of Salsa music utilized by dancers. Rather, New York Salsa closely ties into a specific style of music, and the timing of the dance is based on the bass guitar and the conga drum's tumbao pattern. Mambo always follows the 'On 2' pattern and doesn't encompass the same beat. Commonly, New York Salsa is referred to as Mambo, although this isn't entirely accurate.