PAF is not just the way you discribe something hitting something else. It is also used to define a portable application file. These are self contained executables that you can use for mobile versions of your favourite browser.
One of my personal favourites at the moment is Chrome, it’s fast, light, and behaves the way I want it to. Better still it incorporates flash into the code. This means that I can view flash content without it being installed on the computer I’m using.