Cookie
Cookie is a small piece of data sent by a web server to a web browser. The browser stores this data in a text file. This data is sent by the browser to the web server each time it requests a page from that server.
Cookies store information like your site preferences or history so that they can customize the page for you, every time you request it. So that information is usually not what attacker cares about. Cookies are also used to store information that uniquely identify the user such as the Authentication Ticket. That's more luring to the attacker