What is "open-graph"

The Open Graph Protocol standard enables web pages (Urls) to become rich objects and integrate with the social graph. Through this pattern, a web page will represent the profile of real-world objects such as movies, bands, football teams, companies and many others. The implementation is simple and done through metatags that in this context we call properties. Some of them are required, others optional, recommended and specific for videos, audios and games.

Link to the official documentation: Open Graph