salsa just means "sauce" in spanish. so, basically, you can have like 100 kinds of salsa.
if you make it with tomatoes, onions, chiles, cilantro, and lime juice, and puree it smooth, it's liquid. if you just roughly chop all that stuff and mix it together, it's not liquid. usually they call this "pico de gallo" or "salsa cruda." cruda, incidentally, means "raw," implying that other salsas are cooked, which they usually are not, confusing the issue even more.
check out mark millers salsa book or rick bayless' salsa's that cook. both are great books and will give you a good understanding of how diverse the world of salsa can be.
but....if your only experience with "salsa" is like old el paso or taco bell brand jarred sauces, then this is new.
next week we'll explain why some things are called "mustard" but they are brown and not vibrant yellow and have little specks in them and don't come in squeeze bottles.