Founded by Google, Microsoft, Yahoo and Yandex, Schema.org is a collaborative, community activity with a mission to create, maintain, and promote schemas for structured data on the Internet. There are different types of schema including those for creative work, events, organization, person, place, and product.
Schema can be written in Microdata, RDFa and JSON-LD format. Google prefers the JSON-LD format for schema. If you have no knowledge of writing schema code, then you can use Google Search Console's Data Highlighter Tool to generate schema tags. You need to simply point and click on different elements on your website using the tool.
To check the schema code generated, you can use Google Structured Data testing tool.