

For your layout preferences, colours, other UI options, states (what ‘back’ means), things like that, usually.
If you have an account, what page you were on last, your history so it can give you related items, and other ‘convenience’ features.
Less ethical sites use them to advertise to you, and (more rarely) some scammers use them to scam you.
Most are benign, but some are not.








Oh, then the dipshit is definitely going to try it.