a.k.a. session cookie
A small file that tracks and records where the user goes on the Internet. Internet advertising companies later will use this gathered information to benefit their own business purposes. Generally, users are unaware of the "tracking cookie" that is downloaded onto their computer, as they are not asked permission for the download to occur. Tracking cookies have no user benefit and are generally harmless. If a user is concerned about their privacy, anti-spyware programs do exist to remove these tracking cookies.
NetLingo Classification: Technical Terms