The IVR (Interactive Voice Response) is an automated system that interacts in real time with users who contact the telephone channel. IVRs enable communication with a computer through tone of voice, using prerecorded messages, configurable voice menus or number key options, without the need for human intervention.
If you use an IVR as a means of contact in your organization, you can integrate it with the Voice channel. For example, when a user communicates and is served by your IVR, among the available options it will provide one, which when checked will refer them to a Voice flow, where the conversation with the virtual assistant will continue in voice format.
Below you will find useful information about the IVR, if you connect it with your Voice channel 
a.You can integrate with any type of URA or IVR as long as you have the SIP protocol.
b. You can do a partial implementation, only in some verticals or channels, using the IVR as a filter. Communication would begin through the IVR and then forward the call to Voice.
c. The content of a conversation is not transferable from the IVR to Voice, since it is not saved or transferred information that comes from the IVR.
d. On the other hand, Voice is a voice channel, which transfers to channels of the same format. For example, if you use Live, you must keep in mind that it is a text channel, so it does not apply to transferring either the content or the conversation.
e. If you do not have an IVR system, you can still implement the Voice solution through a virtual number.
Read here about the different ways to connect Voice.
Other key concepts
● SIP (Session Initiation Protocol): communications protocol used to start, change and end communication sessions on IP networks, such as Voice and video calls.
● SIP Trunk: service that uses the SIP protocol to set up Voice over IP (VoIP) communication between a telephone exchange (PBX) and a VoIP service provider over the Internet.
● IP (Internet Protocol): main protocol used to send and receive data over a computer network. It is the basis of the Internet and digital communications networks.
● URA (Unified Resource Allocator): refers to a system that manages and allocates resources in a unified manner, such as telephone lines, to optimize their use.