We recently came across this screencast that Chris made: Is your Avatar a Gravatar? and we think he did a terrific job of breaking down what gravatar is, and what it does! It’s really awesome
The only thing that we’d like to mention is that gravatar is not specific to WordPress, developers are free to use gravatar for anything. We’ve seen gravatars in non-blog web pages, in lots of different programming languages, and even in desktop applications!
So…
*IS* your avatar a Gravatar?