VVJ Core is the shared foundation for the VVJ (Views Vanilla JavaScript) family from Flash Web Center - a set of Drupal Views display formats that turn list content into interactive front-end components (accordions, carousels, slideshows, tabs, hero banners, lightboxes, and more) using modern vanilla JavaScript (no jQuery).
If you are new to Drupal: a View is a configurable list of content (articles, products, team members, etc.). Each VVJ pattern module adds a new Format option on that View so visitors get rich interactions without custom coding. VVJ Core does not add a format by itself. It is the engine room that all VVJ pattern modules share starting with version 2.x.
What problem does it solve? Before v2, every VVJ module duplicated the same PHP services, Twig helpers, and JavaScript utilities. VVJ Core centralizes that code once - smaller downloads, faster security fixes, and a consistent accessibility baseline across the whole suite. When you install any VVJ pattern module v2.x, you also need VVJ Core on your site.