Collections are described in finding aids. Some finding aids describe a collection in general, without an inventory or list of contents. Frequently, you will find a listing of series, sub-series, and folders. Some very detailed finding aids will list individual items.

Most archival collections organized into groups of similar materials called "series", and sometimes further organized into smaller groupings called "sub-series". Series and sub-series are often ordered by subject (e.g. "Administration" or "Medical institutions"); form (e.g. "Correspondence" or "Photographs"); or date. Organizing collections into series and sub-series makes the contents easier to search through and find relevant material.