The goal when writing Beginning SUSE Linux was to make it as readable as possible while providing the facility for readers to learn at their own pace.
Throughout the book, you'll find various types of notes and sidebars complementing the regular text. These are designed to provide handy information to help further your knowledge. They also make reading the book a bit easier.
A note is designed to provide an important piece of information that you should know and that will help your understanding of the topic being discussed.
A tip is something that will help when you need to perform the task being described. Alternatively, it might be something that can make your life easier when using SUSE Linux.
A caution is something you should certainly pay attention to because it warns of a hidden danger or particular caveat that applies to the topic being discussed.
In the sidebars, I take a few moments out from the main body of the book to explain something that you should know, but that isn't vital to an understanding of the main topic being discussed. You don't need to read the sidebars there and then; you can return to them later if you wish.