"Reference is providing assistance by using expertise in response to an information need."
"The interaction is initiated by an individual or group of people working together. This includes a library worker recognizing an apparent information need and seeking to assist with it. Reference work aims to ensure that library users can find the resources they need when they want them." From the Reference and User Services Association, a division of the American Library Association https://www.ala.org/rusa/guidelines/definitionsreference.
The "reference interview" is a conversation between a member of the reference/help desk staff and a library user for the purpose of clarifying the user’s needs and aiding the user in meeting those needs. The interview process involves being approachable; asking open-ended questions; actively listening; showing understanding; assisting with searching and evaluating sources; and concluding with appropriate follow-up and instructions.