What are the uses of Microdata and Schema?

[ecampbell]

What are the uses of Microdata and Schema?

[danni]

The main reason is why HTML tags tells search engines what the page is about, richer search results, better search rankings.

[johnwiliam5946]

In the past, web bots were content to read your headings and content to decipher what it is that your page is about. Now, you can also annotate your content with specific machine-readable labels in order to take away as much ambiguity as possible for your non-human visitors. While Microdata is a standard that is in its infancy, Google has already started to use it as another way of providing rich search results back to the user.
Schema is a specific vocabulary of tags (or microdata) that you can add to your HTML to improve the way your page is represented in SERPs.