JSON-LD

JSON-LD allows us to add semantic information to JSON that's missing normally.
It is used to provide structured data to search engines. This enables them to better find a matching result for a search query, but it also helps to display fancy stuff on the results page.

Example:

<script type="application/ld+json">
 {
  "@context" : "https://schema.org",
  "@type" : "Article",
  "name" : "JSON-LD and SEO",
  "author" : {
    "@type" : "Person",
    "name" : "John Doe"
  },
  "datePublished" : "2020-10-05",
  "articleBody" : "JSON-LD can improve your site’s SEO performance because it helps search engines understand what a page is about. It also helps your site stick out in the SERPs, helping to improve your CTR.\nMajor search engines like Google encourage SEO specialists to use JSON-LD to improve their performance.",
  "publisher" : {
    "@type" : "Organization",
    "name" : "CompanyABC"
  }
}
</script>

Google has made a helper for this structured data: Structured Data Markup Helper - Search Console Help