The word "reference" is usually a noun. A reference is a person or a thing with authority that provides information or supports an idea or a claim about something.
You need to provide three references on the job application form. (References, in this sentence, are the names of people who have a professional relationship with you.)
Do you mind if I use you as a reference for a job I’m applying for?
This is a very good reference book. (The word "reference" in this sentence is an adjective.)
A dictionary is a reference book.
This young man has a question in reference to the fees that are required for a membership.
Tanya made a reference to a nightclub that I’m not familiar with. (make a reference = mention; say)
Please try not to make any references to his past.
What is this in reference to? (This question is often asked when someone has a question or some situation is being addressed.)
A dictionary is a reference book. We depend on dictionaries to provide some authority when studying a language.