Things are much easier when they works synchronously, you just ask for what you want and thats it, but with flash you always have to count on with asynchrony. For example you are waiting on some requests to complete or 3rd party to log you on etc. The issue is, you know you want to execute something, with custom properties, but you have to do that just after some asynchronous event dispatched. E.g. you want to update status with some message, but you need to connect to facebook first. Here comes the handy Callbacks class. What it does is, it stores your wishes and executes when things are prepared.