The categories menu on the left-hand side shows the top categories under which the documentation articles are classified. Within each category, you have several options for looking up articles; you can filter them by tag, by level of difficulty (basic, intermediate and advanced), and by intended audience (analyst or developer).
The Search By Tag
feature allows you to search all the website content by tag and by type (Documentation articles, Events & announcements, Forum discussions).
The Doc Viewer allows you to view documentation articles individually in a more printer-friendly and bookmarkable format. To view a doc article in the Doc Viewer, browse the doc categories and click the file icon in the right hand side corner of the title box as illustrated below.