The text discusses validating data in a Ruby application using Active Model Validations, specifically for a Google Sheets-based database. It covers the basics of validation, including out-of-the-box validations and custom validations, as well as how to implement them in a Rails application. The author provides a step-by-step guide on how to refactor the application to use ActiveModel Validations, including creating a `UserDetails` class with validations for name, email, and phone number. They also show how to implement a custom validation using the Twilio Lookups API to validate phone numbers. Finally, they demonstrate how to display error messages in the view to provide feedback to the user if their input is invalid.