Salsa On-2 — the New York / mambo timing — breaks on the second beat instead of the first. It feels slower and more grounded than On-1, sits deeper in the music's percussion, and is the house style of the East Coast and most congresses. On-1 dancers can usually feel the difference within a song; switching takes a few lessons, not a rebuild.

If you're new to salsa entirely, On-2 is a fine place to start in an East-Coast city — learn it where it's the default. If you already dance On-1, take a short On-2 series rather than self-teaching; the break is a feel, not a rule you can read.