Structured data in your web pages is a great way to tell Google what’s actually in your site. Rather than forcing their search spider to guess whether a certain block of text is your company’s name, address, or phone number, you can mark it up with special HTML attributes that only search engines will understand. Google will also add this information to its search listings for your site, when it’s relevant to do so.
To encourage webmasters to adopt this, Google has just released a Structured Data Markup Helper that will slurp up the exact HTML of any page you give it and add structured markup to whatever text you highlight. At the very least, it saves you the trouble of going to their structured data testing tool more than once.