Salsa's vary in texture, ingredients, preparation, flavors, and just about any other way I can think of. Basically, the word salsa just means 'sauce'. Many on here are describing a few main types. The canned or bottled stuff (sorry...but no self respecting lover of real Mexican food would ever use that swill); Pico de gallo (freshly chopped up tomato, onion, cilantro, etc. Almost a chunky thing more than it is a 'sauce'); Salsa Verde (green salsa made with tomatillos); and Salsa Roja (red salsa).
My Mexican girlfriend makes great salsa using just the basic, FRESH ingredients she gets at the Hispanic market. She also uses a grill (or sometimes the oven broiler) to prepare some of her ingredients. As for a recipe that somebody asked for earlier? Well, sorry. She, like many old style Mexican cooks, does not keep a recipe per say. She uses taste and the ingredients that were passed down from her mother/grandmother. I've actually never seen her write down or read a recipe for any of her dishes. Somebody once asked her for a salsa recipe and all she could tell them was a handful of this....a pinch of that....three or four of these....etc. Usually it gets lost on the person trying to figure it out.
She also makes her own tortilla chips to dip into the various salsas. Very tasty and is nothing like the store junk.