It's a fuzzy line-- the old adage "a language is a dialect with an army and a navy" is more or less accurate. If you're the official language of a country or religion, or are used extensively in business or politics, you get to be "Standard". If you're only spoken by a sub-national cultural group, or appear only in "informal" media and popular culture, you're just a dialect. The distinction itself actually is controversial, see
http://en.wikipedia.org/wiki/Variety_(linguistics)Not that there's anything wrong with having a standard language for business or politics, as long as you don't think that says something about people who grew up in the wrong place or class.