Structured data, otherwise known as schema markup, is often referred to as the "language of search engines". It is a standardized format for providing information about a page and classifying the page content. It helps search systems understand your content more accurately, which means users will get more relevant results.
Structured data can also be used by Google to create rich snippets, which are enhanced search results that provide more information about a website or webpage. Rich snippets can include information such as ratings, prices, availability, photos.
Manually structured data
Webmanager provides tools to insert Structured data into your pages using JSON-LD format.
Identify the data that you want to markup: First, you need to identify the data that you want to provide structured data for. This could include information such as the name of a person, the address of a business, or the rating of a product.
Create a JSON-LD script: Once you have identified the data, you need to create a JSON-LD script that includes the structured data. The script should be added to the head section of your HTML document using a script tag with the type attribute set to "application/ld+json". Here's an example:
Dynamically available within Single-Review rating widget
Results in: 
Backgrounds
- https://schema.org/
- Examples of schemas for rental accomodations: https://schema.org/docs/hotels.html
- Information provided by Google: https://developers.google.com/search/docs/guides/intro-structured-data
- Open Graph docs - http://ogp.me/
List of available Structured data types/fields