Rich Snippets Rich snippets—detailed information intended to help users with specific queries. For example, the snippet for a restaurant might show the average review and price range; the snippet for a recipe page might show the total preparation time, a photo, and the recipe’s review rating; and the snippet for a music album could list songs along with a link to play each song.
From this page: https://support.google.com/webmasters/answer/99170?hl=en
Schema HTML tags, that webmasters can use to markup their pages in ways recognized by major search providers.
From this page: http://schema.org/
Rich Snippets are Google's own wording for the snippet of information that can be given to them when using a markup from the likes of Schema.org (Microdata).
I hope that explains this a little?
-Andy