Cookies are small text files, or bits of information left on your computer by websites you have visited, which let them 'remember' things about you.
From a security perspective, cookies are unlikely to be used maliciously against you as they are just text read by your browser. They don’t contain any code that could be executed. However, websites are able to gather a lot of information about you and your website activity.
If you have concerns about how this might impact on your privacy, you could consider regularly clearing the cookies from your computer or device. Some browsers let you block them altogether. But note that this could affect your experience of some websites.
Visit your browser vendor’s website for more information on privacy and how to manage cookies.