Tracking your browsing habits can be tracked by means other than cookies.  Cookies can be blocked or deleted.  Advertisers have found other ways to accomplish their tracking goals.

Have you ever wondered why once you look at a product online you seem to see ads for it on every site you visit?  Often the ads are even further targeted to your specific tastes and interests.  How do they know what you’re looking at and what things you’re interested in?

There are multiple ways the companies that serve ads on the internet are tracking your browsing habits.  They use cookies, device fingerprinting, and cross-device tracking to build a profile on you.  Not all uses of these technologies are necessarily bad.  Cookies allow sites to remember your username, what you left in your cart, and other preferences you might have.