Cookies are small text files that websites send to a visitor's computer or mobile device while they are browsing. These files store information about the user's activity and preferences, enabling the website to remember information about the visit, like login details, language preferences, and other settings. Cookies play a crucial role in enhancing user experience by personalizing content and remembering user preferences. They are also used for tracking user behavior for analytics purposes and for targeted advertising. However, with growing privacy concerns, websites are now required to obtain user consent for using cookies in many regions.