The Study Binder contains documents associated with the study and the selected site. Some of these documents will be for reference only, and some may be blank templates provided to the site to be completed on a per site or per Site Team Member basis. Documents in Subject Binders are not tied to a specific subject, those documents belong in the Subject Binders Tab.
The Study Binder tabs along the left-hand side, as well as the sections within each, are customized by your administrator to match the needs of your study, and will vary from the example screenshots in these help articles. (If you are an administrator, check out the "Configuring SourceDrive" section for details on how to customize Study Binders and Subject Binders.)
Clicking a section within a binder will open the section and show you the documents within the section. 
Once within a section, clicking another section will take you within that section or clicking a document name (such as "Consent Form" in the image below) would open that document.
You can also click the breadcrumb above the name of the current folder (in the example below it's "Regulatory Binder") to navigate back up to sections you came from. 
Clicking another Study Binder tab will bring you to the sections of documents within that binder. In the example below, we've clicked the "Pharmacy Binder" tab and now can see all the sections and documents inside that binder. 