What's the difference between an auto-attendant and an Interactive Voice Response (IVR)?

While one could easily argue that an auto-attendant and an IVR do basically the same thing—automatically route calls without the need for a live agent or operator assistance—they remain distinct based on their capabilities. Auto-attendants typically offer callers a finite number of branching, options—in other words, they connect callers to designated extensions, based on a spoken request. IVR systems, on the other hand, offer an added level of interaction with the caller in order to obtain a certain end result. In other words, auto-attendants work to match a spoken request with a name and number in the system's registry and strive for accuracy. IVRs work to interpret what the caller is trying to accomplish, and then place them in a bucket (pay a bill, check a balance, and so on), where additional dialogs can direct them into sub-buckets that will allow them to conduct the necessary...