The tutorial discusses how to send domain renewal and expiry notifications using Namecheap API and Twilio SMS in PHP. The prerequisites for the tutorial include having a PHP installed, a Twilio account, a Namecheap sandbox and production accounts, Composer, and setting up the Namecheap API access. The code uses the Namecheap PHP SDK by Maksym Karazieiev to interact with the Namecheap API. The application creates virtual domain names in the sandbox environment to simulate how the API calls would work in production. It includes functions for checking domain name availability, registering a domain name, renewing an expiring domain, getting contact information of the requested domain, sending SMS notifications using Twilio API, and sending all notifications. The code is tested by creating domains in the Namecheap sandbox account and testing the notifications by hitting the URL base_url/index.php in the browser.