** In this updated post, Kyle Kelly-Yahner explains how to build a simple group messaging application using ASP.NET MVC and Twilio. The application has three main concepts: group members, commands, and messages. Members can join the group by sending the command START to the group's Twilio phone number, while leaving the group requires sending the command STOP. As users send messages to the group's Twilio phone number, Twilio initiates a POST request to the ASP.NET MVC application, which processes the message and returns a response to the original sender via TwiML commands. The application uses REST API to broadcast text messages to group members. Kyle highlights that the concepts used in this application can be easily applied to other programming languages or frameworks.