Homebrewers - Whats in the fermenter?

The only downside to using table sugar is that sucrose is a disaccharide of fructose and glucose that the yeast has to break apart, then convert the fructose into glucose before it can metabolize it. That's why most people use corn sugar, being pure glucose it can be metabolized without any extra work. You can use DME, but it takes more of it since it's less fermentable, as well as being more expensive to start with.