This includes banner retargeting. When you visit a new website, the code drops an anonymous browser cookie to that website. The next time you browse the web, the cookie will let the retargeting provider know when to present the ads, ensuring that the ads are targeted to people who have previously visited the website.
Some cookies are more sophisticated. They might record how long you spend on each page on a website, what links you click, even your preferences for page layouts and colour schemes. They can also be used to store data on your shopping cart, adding items as you click. Generally the role of cookies is beneficial, making your interaction with frequently visited sites smoother.
You can change how cookies are stored on your machine by clicking on the Tools menu in your Internet browser.
As always, ensure security measures are in place to protect your devices and only connect to secure websites. For more information on cookies, visit this link.