Subject headings are a formalized way of of searching library catalogs. The right subect heading can help you get to information more quickly.
For example, nutrition can be described using the following terms:
You could search the library catalog for all those keywords. Or, use one subject heading to find all of the library's materials about nutrition, e.g. search using just the term "nutrition."
Who determines subject headings? The Library of Congress. Copies of the complete set of the Library of Congress Subject Headings are available at the Reference Desk.
To find books on program evaluation and planning, consider searching with the following subjects:
Use the advanced search function of the PSU Library Search to enter subjects.