The tutorial covers building a simple calculator with HTML, CSS, and JavaScript. It begins with a basic HTML structure linked to a CSS file for styling. A container div is created and styled with a background color. Inside, a calculator div contains a form with input elements: a text input for displaying results and buttons for operations. Buttons include AC for clearing and others for numbers and functions like addition and multiplication. The process demonstrates adding these elements and testing the calculator's functionality, such as performing calculations and showing results.