Gravatar (which stands for “Globally-recognised Avatar”) is a service that provides globally-unique Avatars.
What is an Avatar?
Hmm, ok you say, but what is an Avatar in the first place?
Well, an Avatar (apart from being a film and a Hindu term referring to the appearance of a deity descended from heaven to earth) is a computer-users representation of him/herself or an alter ego (see Wikipedia definition). Most avatars are far more ingenious than mine (see right) and are often graphical representations of an object representing the person rather than a plain old photo, but their purpose is basically to represent you in graphical form anywhere on the web where your posts and comments appear.
What is a Gravatar?
Gravatar takes things one stage further and enables you to register an image as ‘belonging’ to an email address. Then, wherever your email address is used to post website comments your Gravatar will appear too. WordPress, as well as many other blogging tools and other websites, will automatically look for a Gravatar for you when you post a comment, and display it next to your posts and comments. With one registration at Gravatar you can add any number of your email addresses and assign the same, or different, images to each email address (which might be useful if you have a serious, and a less serious, persona depending on the forum or blog you are contributing to).
Just in case you’re not convinced, there are apparently 29,000 avatar images served every second of the day! Now that’s impressive.