Categories provide a hierarchical taxonomy for classifying items within an archive.
Categories are more typical of museum systems than archival systems, and are seldom used in large archives. However, small archives typically include ephemera as well as archival records, and categories are frequently used as the primary organisational system for this type of item, often as an alternative to a standard series hierarchy.
If categories have been used, you may browse the category tree to locate associated items.
Although categories are widely used in small archives, they are not mandatory. If an archival catalogue does not use categories, you may find that menu options for browsing by category are not available.