system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What are cookies and why do websites ask me about them?
gpt
At its most basic, a cookie is a small text file stored on your computer, which is associated with a specific website and can be read by that website. When they were first introduced, they were designed as a way to "save state": for example, if a website allowed you to change the font size (for example), that setting could be saved in a cookie so you wouldn't have to change it every single time you visited the site: it would "remember" your setting.

However, since then, cookies have been used in more sophisticated ways; they can, for example, track which pages you visit, and this information can be read by an ad agency so that they can run ads based on what websites you visit frequently.

Although this is usually benign, some people find it worrisome. This is particularly the case in, for example, eastern European countries, which spent nearly half the 20th century under governments that regularly spied on them -- they're not comfortable with the idea of a central database holding information about their browsing habits.

So the European Union passed a law requiring all sites that use cookies to inform visitors of that fact. That's why you're constantly being asked to confirm that you're happy to accept cookies.

If you're not in the EU, of course, this law doesn't apply to you; but many sites might still show the dialogue to everyone, simply because it's easier.