This tutorial explains how to send SMS messages from an alphanumeric sender ID using C#, .NET, and Twilio Programmable SMS. An alphanumeric sender ID is a unique identifier composed of letters and numbers that can be used instead of a phone number to send SMS messages. This approach allows for one-way messaging, which is useful for scenarios such as notifications, alerts, and verifications. The tutorial covers how to configure an alphanumeric sender ID in Twilio, set up environment variables with the necessary configuration elements, and write C# code to authenticate with Twilio and send an SMS using a Messaging Service.