I want to fetch and display users info on page from db when someone goes to the url https://example.com/{username}

I have user information in the database table. I want to fetch and display the user's info on the page from DB when someone goes to the URL https://example.com/{username}. But I am confused about how to get it done since the https://example.com/{username} page doesn't exist. I am using PHP and MySQL. I am in the learning phase. It would be nice if someone could tell me what I need to get this done and what am I supposed to learn for this.