SharePoint documentation (TechNet) is a glossary of features and functions that stretches on for somewhere around 10,000 pages, with literally no rhyme or reason.  In order to understand exactly what these features are and how they might/should be used, we created a highly useful logical architectural diagram of SharePoint that groups all features and capabilities into a logical structure to simplify learning, and communicating about SharePoint.  You will find this architectural structure and the parts and pieces that belong in it a highly practical tool to explain and understand exactly what SharePoint is and does.