A conceptual introduction to version control

Version control is a commonly-used, essential tool, but one that often confuses beginners.  I often find myself often repeating the same explanations about version control concepts and the same advice about best practices -- especially for people who are new to distributed version control.  I haven't found a good source for this information, so I have written it up in a webpage that I hope others will find useful:  http://homes.cs.washington.edu/~mernst/advice/version-control.html