What constitutes a draft beer, and how different is it? I see this term plastered on beer cans, but I have no idea what it means, or how it affects the beer's taste.
When you see this term plastered on beer cans, then it means that it's a
Canned Draught. The can contains a widget. This widget was invented by Guinness in order to let consumers drink a
Draught beer at home. This differs from a typical can in that the beer is usually carbonated by forcing CO2 directly into the bottle/can or intermediary vessel, or by "bottle conditioning" (leaving live yeast in the beer and adding something for it to eat, creating CO2 and more alcohol).
Everyone on this site should be thankful for Guinness for having invented the widget!
Simply put, a draft (or draught) beer is one that uses a mechanism to push the beer from it's container (barrel/keg or can.) Typically the beer is pushed using gas, or drawn via a partial vacuum.
A regular (non-draught) beer is a beer decanted without any special mechanism. For example a beer served directly from the bottle or a beer served from a tap inserted into the base of the cask/barrel and gravity fed.