In the most general sense, air conditioning can refer to any form of technology that modifies the condition of air (heating, (de-) humidification, cooling, cleaning, ventilation, or air movement). In common usage, though, "air conditioning" refers to systems which cool air. In construction, a complete system of heating, ventilation, and air conditioning is referred to as HVAC.
Before calling to schedule your appointment, it may be helpful to familiarize yourself with the air conditioning equipment that you have. Make sure you know at least the brand name, the model and the approximate age of the system, as well as any warranties that may be in effect—and read through our AC FAQ to see if any of your symptoms sound familiar.