Cookies are small files stored on a device, such as a computer, a mobile device or any other device that can store information. Cookies serve a number of important functions, including remembering  users and their previous interactions with a website. They can be used to keep track of items in an online shopping cart or to keep track of information when details are inserted into an online application form.

Authentication cookies are also important to identify users when they log into banking services and other online services. The information stored in cookies can include personal data, such as an IP address, a username, a unique identifier, or an email address.