What is this?

Per the Microformats Wiki:

The vCard standard (RFC2426), has been broadly interoperably implemented (e.g. Apple’s “Address Book” application built into MacOSX).

In addition, many bloggers identify themselves by name and discuss their friends and family. With just a tad bit of structure, bloggers can discuss people in their blog(s) in such a way that spiders and other aggregators can retrieve this information, automatically convert them to vCards, and use them in any vCard application or service.

This specification introduces the hCard format, which uses a 1:1 representation of the properties and values of the aforementioned vCard standard, in semantic HTML. Bloggers can both embed hCards directly in their web pages, and style them with CSS to make them appear as desired. In addition, hCard enables applications to retrieve information directly from web pages without having to reference a separate file.

In short, hCards are a standard way to implement vCards in plain old semantic HTML.

If you would like to easily implement an hCard on your website, try Microformats’ excellent hCard creator.