The WhatsApp Business API from Twilio allows developers to send messages to users on the popular messaging app, making it accessible from shell scripts. To follow along with the tutorial, developers need a Twilio account and a copy of cURL installed on their computer. A smartphone with an active WhatsApp account is also required for testing purposes. The Twilio WhatsApp sandbox provides a way to develop and test applications without requiring production access. Developers must authenticate against Twilio services using stored credentials and then send a WhatsApp message using the Twilio API. Once authenticated, developers can use cURL to send messages on WhatsApp, with the option to add more functionality in future tutorials.