Voice Proxy is also known as Masked Calling. It refers to the technique used to protect users' private information by providing an intermediary number so that neither party can see the other's true phone number for voice calls or SMS.
It is especially useful for scenarios where you want to track or control the transaction between two users, for example in a marketplace. Examples of peer-to-peer marketplaces that use Twilio as a Voice Proxy are Uber, Lyft, Airbnb, Postmates and Instacart.
There are two main options to build a Voice Proxy solution: