The about and mentions markups are Homes of webpage schema which explicitly explain to search engines like Google and Bing what matters a page is generally about and what other subject areas are only getting pointed out or referred to. It incorporates references towards the Schema.org and Google documentation for https://bookmarkingdepot.com/story19350430/the-ultimate-guide-to-json-schema-is-not-supporting-please-check-your-json