Just like the word upgrade means different things to different people, the word suite does too. All to often when I check into a property and told I've been upgraded, I'm hard pressed to see what constituted the room to be classified as such (did make me feel sorry for those that weren't).

To me a suite is a larger room with maybe a separate sleeping area. To some of the lower-end brands a suite is a room with a refridgerator and maybe a microware, even it was just wheeled into the room.

I don't think there is a standard definition as to what constitues an upgrade across all the brands. Each property is pretty much able to define the rooms as they like. Even looking at available rates doesn't mean a higher rate is a better room.