Online catalogue (IPAC) help.

Searching by subject categories (Subject search) allows to display records containing one category inmediatelly.

Categories are in two levels. Clik on the icon of maginfier next to category title and search records from this category.
If you open the category by clicking on the icon „arrow“ , you will also be able to check more sub-categories in other categories. Click on the button Search and records search and display will start.

Subject categories are usually created by library as a universal list of subjects that can be used in different libraries.
It can happend that you wil not find any records in your library for the category you are interested in.