Schema markup also known as structured data markup, is a set of tags that communicates with search engines. Schema tells search engines what information is on the webpage, whether it's an image, a blog post, a title, or your company's contact information.
Schema organizes data into two categories, Itemtype and Itemprop. Itemtype is the thing you are defining, such as an organization or event. Itemprop is the properties of the Itemtype, such as it's name, title, or description.
There are two options for applying schema to your website. Site-wide Schema goes into the header and footer of your website and is used on every page. It is perfect for maintaining your company name and contact information so that it remains uniform throughout all of the pages on your site. Object-specific Schema is used for content that does not repeat on multiple web pages. Some examples of where Object-specific Schema is used are on images, videos, and downloads.