Well, it's just one of the many names for sugar in the raw. You know, the kind of sugar that won't (ever!) dissolve in your coffee.
Turbinado a.ka. demerara a.ka. sugar in the raw won't melt in high heat, so these granules make great cookie toppers. Give dough balls a roll through some of this stuff before baking, and you'll get cookies that have a nice crispy, shiny exterior--kind of like a candy shell.