What Defines a Substyle?

Lately, I feel like every time I turn around, people are talking about new substyles of lolita. From multi-street-fashion mash-ups, to the long-defined gothic, classic and sweet, to declaring a style based on the theme of a print. So, it's been making me wonder what other people consider to be substyles of lolita, and when something really "counts" as a substyle.