If you are new to Schema.org markup, you are not alone. Schema.org is a joint project between Search Engine giants Google, Bing, Yahoo! and Yandex so it is fast becoming an important addition to your website to help your content get indexed.
In summary it provides clear structured information to the search engine spiders about rich content such as events, people, places, products, reviews and media content. A full list of current Schema.org types can be found here.