A cookie is a small text file that websites store on your device to remember information about you. Cookies serve various purposes: keeping you logged in, remembering preferences, tracking shopping carts, and analyzing how visitors use websites. First-party cookies come from the website you're visiting; third-party cookies come from other domains (often advertisers) tracking activity across multiple sites. Privacy concerns about tracking cookies have led to regulations requiring websites to disclose cookie use and obtain consent. Browser settings allow users to block or delete cookies. Government websites use cookies to improve user experience while balancing privacy considerations, with policies explaining their cookie practices.