This document discusses how database queries are used in a social media application called MySocial to retrieve and store user data. It provides examples of functions in the database_queries.php file that query the database to get a username, add a user post, and get all posts for a user. These functions are called from the controller and views to retrieve and display the necessary data to the user. The database stores tables like users and posts that are queried to integrate user information and content into the web application.