system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What are cookies from websites?
gpt
A cookie is just a bit of data that the website stores on your computer to look at next time you come back.  A common and very useful application of cookies is storing what account you logged into so that you'll be signed right back in when you reopen the site.

What gets more ethically dicey is when the cookies are being used to store information about you for things like advertising (e.g. storing that you looked at X and then showing you ads about it) without your consent, which is why you see warnings about using cookies on websites.