The app is set up to allow you to use character sheets, rolls, and chat (whispers/GM secrets perhaps? :D ) while playing an in-person game. So, I get everyone to come over to my house for a game of what ever, we're using a physical map on my table and actual miniatures, but the character sheet can be kept on Roll20 and accessed by everyone through the app and I can have them roll directly off of it so all the bonuses and penalties are accounted for. Especially if I'm playing a math/calculation-heavy game (say Rollmaster), it speeds things up a lot by allowing my players (and myself) to not have to calculate everything manually. I have also experimented with having the app running on my tablet to allow me to keep a character sheet open on it while playing Roll20 on the computer, but for me, just popping the character sheet out into it's own window is easier/better.