Whenever you visit a website, it leaves a cookie that stores the information that you have searched or even typed on the website. The more websites you go into, more cookies will be stored in your web browser. If you try going into a website with dozen of advertisements, you will find out that the website is using your cookies information to display relevant advertisements. For example, I have searched for properties around my area recently. I then went into a US website. Immediately, I was greeted with advertisement about real estate oak island nc.
An even more concerning issue with cookie is that whenever I do online banking, the next thing I find is a spam email telling me that my online banking has been locked and click the following link to unlock. In the past, I would just try to log back in to my online banking, not through the link in the email though. But now, I would just ignore them. I remember that I received an email from Paypal before saying that their email will always greet me by my name. Indeed, these spam emails only greet me by “Dear customer”. Anyway, banks will never ask use to enter sensitive information or links through emails.