What is a custom facet? How does it work?

What is a custom facet? How does it work?

      Custom Facets or Custom Pages are masks for the filtered pages. When a user applies a specific filter or combination of filters, Custom Facets is applied to change the content of the page:

This is a category page with a simple filter by size applied.
      
Same page with a Custom Facet - updated title, added a CMS block in the top of the page.
      What content can be modified with the help of a Custom Facet:
  1. Title and description of the page;
  2. Images;
  3. Top and Bottom CMS blocks;
  4. Meta info, such as Meta Title, Meta Description, Meta Keywords, and the Canonical URL.
      Facets can be applied to a specific category on one or several store views. This way you can broaden or narrow down the application of the Custom Facet.