Twilio Elastic SIP Trunking is a service that connects IP-based communications infrastructure to the publicly switched telephone network (PSTN), allowing users to make and receive calls globally. It offers several advantages over traditional SIP Trunking, including ease of configuration, freedom to manage SIP connectivity, and transparent per-minute pricing. The service can be used with FreePBX, a web-based GUI with an underlying Asterisk-based PBX, and provides step-by-step video tutorials for configuring the service, including trunk termination, origination, and international trunking. Users can create and manage trunks instantly through the Twilio web portal, and the service is built on a connectivity layer of hundreds of carriers worldwide.