We are talking sauce here, not the dance! Salsa in Spanish means 'a sauce'. Salsa has been traced to the Aztecs, Mayans and Incas.
The Spaniards first encountered tomatoes after their conquest of Mexico, which marked the beginning of the history of Salsa. Aztec lords combined tomatoes with chili peppers, ground squash seeds and used them as a condiment served on turkey, venison, fish and seafood.
Unlike traditional sauces, salsa has become a condiment and a dip and even a side dish. Salsa, today can be described as "vegetables or fruits chopped up with herbs and spices and usually chilies and onions." Making a fresh salsa just takes minutes.
A basic formula is: A main fruit or vegetable (most familiar is the tomato, tomatillos but it could be melon, citrus, beans, corn + a crunch (think onions, bell peppers) + spice (finely chopped chilies) + fresh herbs (cilantro, mint, basil, flat parsley + lime juice.
Recipes:
Salmon with fruit Salsa
by Food411's Chef Silvia
Wonderful collection of creative salsa recipes:
http://www.foodnetwork.com/recipe-collections/salsa/index.html