Let start by clarifying the difference. Schema markup or structures data is the code that makes is easier for search engines to read and understand what your website is about. The code can be found at Schema.org which is sponsored by Google, Bing, Yahoo and Yandex. So a website crawls your site and find the schema they use data to then create a rich snippet that a person sees in the search engine results.
What is even cooler about seeing a rich snippet in the SERPs(search engine results) is that you can make your result stand out with things like star ratings, links and more.
Search Engine Land did a study and found that people have noticed a 30% increase in organic CTR (click through rate) when using schema markup.
Let’s look at an example: