Ask Dr. Universe

Asked by Lydia, 8, Essex, England.

Dear Lydia,

A cookie is a tiny file of text that gathers information about you as you browse the web. You might be familiar with cookies if your computer has ever asked if you wanted to turn them on or off.

Let’s say you want to go visit your favorite website. Maybe it is one with cat videos. Humans seem to love cat videos, especially the ones where we are doing something silly.

You open up a web browser and type in the web address, which starts out with H-T-T-P. HTTP is a kind of language the World Wide Web uses to communicate. Browsers can understand this l...