The way i learned twisted was by starting a small project and lots of googling around; the twisted tutorials are sometimes not very clear, its just getting used to the framework and the way it works...
EDIT:
itd also recommend trying to understand what twisted is based on, the whole idea of twisted is to provide event driven programming for python, along with some other features such as asynchronous sockets and web server classes.
A quick explanation of deferreds and callbacks, which is the whole idea behind twisted, is creating an event (deferred object), then attaching a callback to it; then at some point ur going to fire the event, and the callback is triggered with a result (it could be null) from ur event operation. A good example is, if you have a button on a form, you create an event (a deferred object) then u attach a callback, when the user clicks a button, they fire the event, and the callback function is called to handle that event.
i hope this will give u a good general idea of what twisted is and how it can be used in a python environment, there is also IronPython (.NET) which has eventing as well.
~george