Customer calls in your company. Call is answered, not by conventional receptionist but by an electronic receptionist, an automatic attendant. The answer your customer gets is, "Welcome to XYZ Company. Dial the extension number of the department or person you want to reach" by a recorded voice. And thus it goes on giving you options.
This e-receptionist directs you towards getting your query resolved. Who is this electronic receptionist? This Electronic Receptionist is IVR/IVRS or Interactive Voice Response System. With IVRS, the caller to your company gets directions to receive the answer for their query via pre-recorded messages.
Quoting Wikipedia, “Interactive Voice Response System or IVRS is phone technology that allows a computer to automatically detect voice and touch tones using a normal voice phone.” The objective of IVRS is to cut down customer service costs by providing self service to customers and guiding them to the department, person or information that they need.
Modern IVRS / IVR systems enable users to interact through a computer system via two interfaces - the interactive response voice based system (IVR) and now an interactive response web-based system (IWR).