A recipe is a simple document that provides a solution to a problem. It's generally a snippet of code that can be copied and pasted, with a small discussion to give additional information and ideas on how to use it.
If you ever plan on internationalizing your app, you're definitely going to need to know the language and country associated with a user's PlayBook. Not a very difficult task, mind you, but definitely an important one.
Your applications might need to send or receive data over a network connection while they're running. You can use the network status service to determine if a user's BlackBerry PlayBook tablet is connected to a network.
The touch screen is the primary input method on the BlackBerry PlayBook tablet, so you'll probably want your applications to be able to process and respond to touch events.
You can poll the accelerometer sensor on the BlackBerry PlayBook to retrieve accelerometer readings and then convert those forces into pitch and roll values.
You can provide digital goods that users can purchase directly from your applications. These digital goods could be extra content or premium content, such as extra levels for a game.
Users can hold a BlackBerry PlayBook tablet at any angle, including portrait and landscape orientations. You can determine the orientation of the tablet by registering your application to receive orientation screen events.
If your applications need to include an audio component (for a music player or a game with a soundtrack), you can play an audio file in the background and perform other application tasks while the file is playing.
Your GPS application might need to know where your BlackBerry PlayBook tablet is in the world and where it is going. You can find its position, heading, and speed in the world.