ALA Reference & User Services Association (RUSA) defines reference services as:
Reference transactions are information consultations in which library staff recommend, interpret, evaluate, and/or use information resources to help others to meet particular information needs. Reference transactions can include informal instruction or exchanges that provide assistance with locations, schedules, equipment, supplies, or policy statements.
Reference work includes reference transactions and other activities that involve the creation, management, and assessment of information or research resources, tools, and services.