The Views module uses a series of hooks to retrieve data that it then uses to represent ways to interact with the database. One of these is the hook_field_views_data hook, which processes a field storage configuration entity and registers its data with Views. The Views module implements this on behalf of the Drupal core to add relationships and reverse relationship, for Entity reference fields.

Since Entity reference fields have set schema information, Views can dynamically generate these relationships by understanding the field's table name, destination entity's table name, and the destination entity's identifier column.