ACD routes customer calls based on preset rules (such as prioritizing VIP callers or routing calls based on agent skill).
A virtual receptionist (also called an automated attendant or auto attendant) lets callers press a button to choose where they’re routed. This could be an internal extension, an external device, or a recorded message.
The main difference is that ACD telephony routes incoming calls automatically, while virtual receptionists provide options for callers to route themselves.