What is a Finding Aid?
A Finding Aid is an inventory of the materials in a collection; in many cases, it will give a complete list of a collection's contents by box or folder. So, if you are interested a large collection, such as the UAW's papers at Reuther Library in Detroit, it is extremely helpful if there is a finding aid that will tell you which box or folder would be most relevant to your research. Finding aids will generally give a list of correspondents, as well as the organizations, projects, and topics that are in a collection.
In the best case scenario, a collection is fully described in a finding aid that can be searched through a database like WorldCat or Archive Finder. In many cases, however, there might only be minimal description of the collection, and you will need to contact the library directly (or visit the collection in person).
Often you will find finding aids online through a library catalog.