Our coverage of the sample code was not meant to be extremely thorough; just enough to give you an idea how it works. We'll be covering OOP concepts in more detail throughout the chapters, so if anything is bit unclear, don't worry too much.
As OpenLayers is a library and provides functions for you, it is important to know what those functions are and what they do. There are many places to do this, but the best source is the API docs.
The API documentation is always up to date and contains an exhaustive description of all the classes in OpenLayers. It is usually the best first place to go when you have a question. You can access the documentation at http://dev.openlayers.org/docs/files/OpenLayers-js.html. It is continually updated and contains a wealth of information. We will constantly refer to it throughout the book, so keep the link handy! Sometimes, however, the API docs may not seem clear enough, but there are plenty of other resources out there to help you.