A cookie is a small piece of data that a website stores on a user's computer to remember information about them, such as their login details, preferences, or shopping cart items. Cookies are sent back to the website by the user's web browser each time they visit the site. This allows the website to personalize the user's experience and provide relevant content. Cookies are typically stored as text files and are managed by the web browser. They can be used for a variety of purposes, including session management, personalization, and tracking. While cookies are generally harmless, they can be used to track user activity across multiple websites, which raises privacy concerns. Users can control how cookies are used by configuring their browser settings to block or delete cookies. There are different types of cookies, including session cookies (which expire when the browser is closed) and persistent cookies (which remain on the computer for a longer period of time).