On-page schema or rich snippet markup is a way to enable search engines to better understand the structured data contained on these web pages which in turn provides better search results to users.

If Google understands the content on your pages, we can create rich snippets—detailed information intended to help users with specific queries.

Rich snippets are additional data displayed within your ad listing that provide a quick glance at what your page offers without forcing the surfer to click.

There are 3 ways to use rich snippet. Google suggests using microdata, but any of the three formats below are acceptable.

    Microdata (recommended)

Google supports rich snippets for these content types:

    Businesses and organizations

Technically this information isn’t strictly PPC, but it sure affects you if you are running or using a product feed for things like Product Extension Ads or Product Listing Ads and the feed suddenly disappears, disabling all your precious AdWords attributes and rendering the Auto Targets tab useless.

This is how a rich snippet looks like:

From where we can get Reviews in our PPC Ads?

Getting reviews to display on your product and text  ads can be acquired from three main sources:

The first and more popular option is via rich snippets reviews,

The second source is through the Product Search Seller Rating extension

And the last and more recent option is via reviews from your Google Places profile page (which is currently only available from AdWords express account but highly likely to be included in AdWords).