Microformats, Microdata, RDFs and so-called Schemas are sets of standards used to mark up particular data in a body of HTML code. For example, one can highlight their company’s name, address, phone number, etc. on their web site using special tags. Such data is often referred to as structured, and has become widely used by webmasters with the development of the semantic Web.
‘What does it have to do with SEO?’ one may ask. Thing is, structuring information on your site makes it easier for the search engines to recognize it. As the result, your site may rank higher in Google and other search engines. At the same time, semantically marked-up data looks more appealing in the SERPs (think of rich snippets), which leads to higher click-through rates and better conversions.
Nowadays, one sees structured data all over the search results. Pretty much everything that’s not a title or a description is semantically marked-up information: a business’s address, phone number and hours of operation, product ratings and reviews, etc.
The difference between Microformats/Microdata/RDFa and Schema.org
There are several sets of standards one can use to mark up information semantically. Semantic structuring is built up on top of existing HTML standards. Among the formats available today are Microformats/Microdata/RDFa, Schema.org, and others.
They differ in syntax and a number of other characteristics, but their purpose is essentially the same.http://www.searchengineoptimizationjournal.com/structured-data-formats/