The help section of this site is broken into two sub-sections:
This section lists important variables and functions that developers will need to refer to when working with the code that runs the CMS. If, for example, you're developing a template and want to find out exactly how the CMS menus are built this section details the functions used to create the menus and all of the options available to you.
This section gives step-by-step instructions for performing assorted tasks related to the CMS. If, for example, you wanted to build a template and didn't know where to start this section will give you a broad overview of the process of designing and building a template.
Using the tutorials does not require you to know everything in the reference section. If a function or variable is used in a tutorial, you can click on its name to see full details in the reference section. It's not necessary that you stop and read those pages as you go along - but please remember that they're available to you if you want to learn more later.