Cookies are small pieces of data that websites store on a user’s computer or device when they visit the site. These data files are typically composed of text and are used for various purposes in web development and online browsing. Cookies serve several functions:

1. Session Management: Cookies can help websites manage user sessions. When you log into a website, a session cookie is often created to remember your authentication status. As long as the session is active, you don’t need to log in repeatedly.
2. Personalization: Websites use cookies to remember user preferences and settings. For example, a website might remember your preferred language, display settings, or shopping cart contents through cookies.
3. Tracking: Cookies are frequently used for tracking user behavior. This can be for analytics purposes to understand how users interact with a website, or for advertising to deliver targeted ads based on your browsing history and interests.
4. Authentication: Cookies can store authentication tokens or credentials, allowing users to remain logged in to a website or application even after they close the browser.
5. Shopping Carts: E-commerce websites use cookies to store items in a user’s shopping cart. This ensures that the items you add to your cart remain there even if you navigate away from the shopping page.
6. Security: Cookies can enhance security. For example, they can be used to detect suspicious or unauthorized activity, such as multiple failed login attempts.
7. Remembering User Information: Some websites use cookies to remember user information, such as your username or email address, so you don’t have to re-enter it each time you visit.

Cookies are divided into two main types:

1. Session Cookies: These cookies are temporary and are stored only for the duration of your visit to a website. They are typically used for session management and are deleted when you close your browser.
2. Persistent Cookies: Persistent cookies are stored on your device for a longer period, even after you close your browser. They can be used for functions like remembering login information or user preferences. Users can often control how long persistent cookies are stored on their devices through browser settings.

It’s worth noting that while cookies serve many legitimate purposes, concerns about online privacy have led to regulations like the General Data Protection Regulation (GDPR) in Europe and the California Consumer Privacy Act (CCPA) in the United States. These regulations require websites to inform users about the use of cookies and obtain their consent before storing certain types of cookies. Users can also typically manage and delete cookies through their web browser settings to enhance their online privacy.