It’s a content entity originally created by the Crocoblock team as part of JetEngine plugin functionality to optimize the WordPress database and store custom fields in a more efficient way. Each Custom Content Type, or CCT, creates a separate database table. Each post entry occupies one row there, unlike the posts (or CPTs) that store information in two tables (wp_posts and wp_postmeta) where each field (not a post) occupies a separate row, so it takes time to crawl through all of them in order to retrieve information for one post.