If you are interested in a theoretical explanation of "on 2" and are already somewhat familiar with the concept, this is for you.
A lot of people ask what it means to dance salsa "on 2", or on the second and sixth beat of the song. This is often called Mambo. Luis Rodriguez wrote an excellent article about how he interprets counting and moving "on 2" for those who want to learn more about it. Here I share with you:
When you're dancing "on 1" or "on 2", you're probably already aware that a complete basic (from first step to last) is eight total counts.( if you're dancing on 1, a "basic" would consist of the following steps (and I've included the steps along with the corresponding count next to it): Left-1, right-2, left-3, (pause or tap)-4, right-5, left-6, right-7, (pause or tap)-8 - and whether you pause or tap is your preference or the preference of who is teaching you.) Your dance is just a repetition of that eight count pattern, over and over again, and as you further your skills, you learn how to throw in turn patterns along with those steps and counts When you are dancing "on 1", and especially if you are from Chicago and you've learned how to mark/check, you've probably noticed by now that you are always going to mark or check on your fourth and your eight count (which also happens to be the same count you tap or pause on.) If you pa! y careful attention to individuals who dance as such, regardless of how smooth or "passionate" you try to make your dance, the style of such dancers is still very punchy, sharp, and distinct. Every step you take is on a distinct count, and never do you start a step somewhere in between those counts. If you did, it would do the dance an injustice and would make the dance seem somewhat odd. Dancing "on 1" is sometimes considered easier to learn because it is very precise.
When dancing "on 2", your "basic", similar to dancing "on 1", is still 8 counts, but the difference is that your steps are as follows: Right-1, Left-2, Right, 3 (Pause for 1 and 1/2 counts), Left-5 (which really starts at 4 and 1/2, Right-6, Left-7. . . Now, for the next basic pattern, when you start on your Right foot again, your 1 is really going to be started half way between 8 and 1. To account for that 1/2 count delay, the 1 count and the 5 count get dragged and extended as the instructors count those counts. So, as you pointed out, the "on 2" instructors will count out your basic like this: "Ooooone, TWO, three, (short pause), Fiiiiiivve, SIX, seven, (short pause), Ooone, TWO, three. . . . and so on. Because of the dragging of the one and the five count, the TWO and the SIX come out really sharp. Not to mention, if you pay attention to those steps, there are distinctive hits that occur on your two and your six. .! . especially when you are listening to Mambo music from artists such as Joe Cuba. Sometimes, it is really difficult for an instructor to explain this to their students. Instead, it is just easier for them to do it. While for the short term, it is more expedient to teach students this way, I've found that for the long term, this is something that always plagues those dancers that are trying to understand what exactly is going on and why exactly the dance "feels" the way it does. The fact of the matter is that even dancing is somewhat of a science. There is "theory" behind it too and much too often, an understanding and explanation of that theory is left out.
For many (not all) that have observed or have started learning "on 2" dancing, they (just as I did) have realized that dancing on 2 seems smoother, more fluid, and seems to "click" with the music just a bit more than dancing on 1. ( hopefully, those with a preference have actually tried to learn both methods. Not suprisingly, I've also learned that almost all (but not ALL) the folks who rather dance "on 1" who have tried to lean "on 2", are the folks that never really learned how to stay on 2 - and I can almost guarantee its because they don't understand the theory behind "on 2"). Part of the reason dancing "on 2", for some, is just more appealing, smoother, and fluid is because when you dance "on 2", by extending that 1 and 5 beat, there is no room for marking/checking. Instead of stepping on each of you eight counts, you are dancing on six of the eight counts, and extending your one and your five f! or a count and a half to make up for that difference. Visually, especially when two "on 2" dancers that truly understand this concept are "going at it" on the dance floor, this allows for a very attractive, sensual, playful, and appealing display.
I understand that this explanation may not make that much sense to you written down. But if I had my congas with me and two clave sticks, or a cowbell, I could explain it to you with some rhythm and with some physical example. Hopefully, my superiors at Latin Rhythms will allot me some time this summer to teach some of these fundamentals at the studio. If not, feel free to contact me, or contact my teacher Maricza, or any of the instructors at the LRL studio. They'd be more than happy to explain this to you, probably in a manner much more conducive to learning than my method. I hope this helps.