Rich Snippets Explained by Google in Tutorial Video

Rich snippets, or microdata, are a great help for search engines and what helps search engines helps their users. All the major search engines got behind Schema.org, which details the microdata standard and the formats that are in use.
Already, search engines use this data for a number of searches, from recipe search to software reviews. More data types will be added in the future, but webmasters need to update their pages with rich snippets to provide search engines with the most relevant info.

Google has put together a series of video tutorials to help webmasters and website owners get started with rich snippets and to understand why they're important.

There are ten videos in the series now, available on Google Webmaster Help's YouTube channel. You can get more info from Google's Help center and check out Schema.org for an overview.