The Folger Catalog at https://catalog.folger.edu contains descriptions of (almost) everything in the collection. Some of the records contain very detailed descriptions, some instead give a more general description of a group of related materials, others are just preliminary records that serve as place-holders until an item can be fully cataloged.
See Folger Catalog Search Tips for more.
Other resources for discovery
Catalogs typically provide bibliographic description of individual items such as books, journals, works of art, manuscripts, objects, etc.
Finding aids typically provide archival description of collections of manuscripts and records, with inventories detailing what is included in each collection.
However, there is some overlap between catalogs and finding aids; collections can be described in a catalog and individual items can be described in finding aids. In general, if you are looking for a published resource or a work of art, start with the catalog. If you are looking for unpublished papers and records, including letters, diaries, collected documents, and the like, start with finding aids.
If you have questions about the catalog, please contact firstname.lastname@example.org.