Microformats are simple conventions for embedding semantics in HTML to enable decentralized development. They are designed for humans first and machines second, using existing HTML standards. Common microformats include hCard for contact information, hCalendar for events, and rel-license for indicating content licenses. Tools like Firefox extensions can consume microformats, and sites like Flickr and Meetup.com use microformats to share information in a structured way. Developers can also build their own applications using microformats.