For example, what is a micro-app? How does it differ from just an app?
It says you can: "Engage with your fans and users by creating micro-apps that allow you to interact in a much richer way than tweets, ads, or email." It's lightweight but enables a richer communication experience. How? Do you have some examples?
Compare it to, say, an SMS. Instead of a bit of text, you get a bit of text, two buttons, a camera button, etc etc etc. So it's richer than a notification, but only by a little.