Categories and tags are important tools in your content management arsenal. You use them to organize your posts and provide a better user experience to your site visitors. If you’re new to WordPress you might be confused about when to use one or the other. This screencast explains the differences between categories and tags, and provides some general guidelines for when to use each type of metadata. As a bonus, this video also shows you how to convert categories and tags. So, if your categories and tags are out of control, there’s still hope that you can restore order to your site.
To bring yourself up to speed be sure to watch the companion screencasts on using categories and using tags.