In this article you'll learn what structured data is and why it matters, and get a high-level understanding of how to implement it on your website.
Contrary to common misconceptions, sitemaps and microdata are not the same thing. A prioritized sitemap emphasizing the most frequently updated and/or important content on your website is indeed helpful, but it will not appeal to Google and Bing’s new movement toward microdata, and in turn, enhanced search engine results listings, or "rich snippets". A sitemap is merely a map of page URLs featured within a site. Microdata like Schema serves an entirely different purpose – to take content within a page, and categorize that data so the search engines can quickly discern what your content is about and better deliver your content to the right searchers using structured data. Schema uses specific verbiage to categorize different types of data. So when a search engine reads a user query and detects searcher intent, it can deliver better, richer results to the searcher.
For example, at its most basic, Schema markups will help a search engine quickly understand if your content is about a person, place, thing, product, event, organization, creative work or review. (There are others - these are the biggest, baddest ones in my opinion.) To delve deeper, if your content is about something like a recipe, you can also categorize parts of that recipe – which part is the description, name, image, ingredients, cook time, type of cuisine, and so on. One possible impact of using Schema markup language (which is essentially simple HTML tags wrapped around existing content on the page) is richer snippets in the search results.
Take, for example, the “cornbread recipe” Google search result below. It shows the image, number of reviews, star rating, cook time and calorie count right on the search results page. Search engines would quickly able to pull those parts from your page to display in the search results, because you've flagged parts of your content as that type of data.
Schema, Microformats and RDFa are all currently acceptable ways to categorize data on the page, but many experts are leaning toward Schema winning out as the ideal microdata vocabulary that will likely be accepted by the major search engines in the future. The three major search engines - Google, Bing and Yahoo - came out in June of last year advocating Schema in particular, though they said that the other formats would continue to be supported.
There is no evidence that right now these Schema markups affect search engine rankings, though multiple search engines (including Stefan Weiz from Bing in a presentation at MozCon 2011 in Seattle) have stated publicly that this new way of categorizing data will become increasingly important. Also, richer search results with more accessible data and images have shown time and again to increase click-through rates to your content, as the searcher’s eye is drawn to concise, visual data. There is no guarantee that the search engines will elect to use the microdata in a rich snippet, but it greatly increases the likelihood.
Essentially, Schema, microformats and RDFa take the guess work out of detecting what your content is about for search engines. It takes easy-to-read content written for people, and translates it to easy-to-categorize data for search engines.
Here's my SlideShare on the topic. Structured Data: Schema, Microformats & the Future of SEO: