A directory table in Snowflake is an implicit object layered on a stage that stores file-level metadata about the data files in the stage. Option B is correct because it accurately describes this concept, aligning with Snowflake documentation which states directory tables are 'conceptually similar to an external table' and store file-level metadata. Option A is incorrect because directory tables are not separate database objects but are layered on stages. Option C is incorrect as directory tables are not primarily about grantable privileges for unstructured data tasks. Option D is incorrect because directory tables are not Snowflake tables designed for storing unstructured files themselves, but rather for storing metadata about files in stages.