Final answer:
The correct answer to the student's question is 'cookie'. It's the small bit of data stored on a client's machine used for tracking and remembering information about the user's session or preferences on a website.
Step-by-step explanation:
A small bit of data stored on the client machine that is passed back and forth to a web server is a cookie. A cookie is a small file that a website places on your device while you visit it. Cookies are used to remember you and your preferences, track your visit, or ensure the security of your connection. For example, when you log in to a website, a cookie is created to keep you logged in as you navigate the site so that you don't have to enter your credentials every time you access a new page.