Cookies are small blocks of data created by a web server while a user is browsing a website and placed on the users computer or other device by the users web browser. They are used to store information about a users browsing activity, such as items added to a shopping cart or login credentials, or to track a users browsing activity. Cookies can be categorized into two types: session cookies and persistent cookies. Session cookies are only active while the user is browsing a website and are deleted once the user closes the session, while persistent cookies remain on the users computer. Cookies can be accessed by the browser user, the site a user is on, or by a third party that might use the information for different purposes. Cookies were originally introduced to provide a way for users to record items they want to purchase as they navigate throughout a website. Today, however, the contents of a users shopping cart are usually stored in a database on the server, rather than in a cookie on the client. Cookies can also be used for logging into websites, making personalized content recommendations, tracking items viewed in an online store, and auto-filling information in forms.

In summary, cookies are small pieces of data that are stored on a users computer or other device by a web browser while the user is browsing a website. They are used to store information about a users browsing activity or to track a users browsing activity. Cookies can be categorized into two types: session cookies and persistent cookies.