There are three types of facets, each determined by the facet’s location in the catalog hierarchy:
Global facets are available to all products in a catalog or set of linked catalogs. In a multisite environment, global facets serve as cross-site facets and are available to all products on all sites.
Catalog facets are available to all products in a catalog or set of linked catalogs. In a multisite environment, catalog facets created on the top-level catalog function as site-specific facets.
Category facets are available to all products in a category or set of linked categories.
Note: Catalog and category facets are sometimes collectively referred to as local facets in the Merchandising and Search Merchandising UI. A catalog or category facet is defined as local when it is being viewed in the context of its parent catalog or category. For example if you define brand_facet for CatalogA, brand_facet is CatalogA’s local facet.