A very small text file (i.e., program code) that is stored on a user’s browser for the purpose of uniquely identifying that browser during audience activity and for authenticating, tracking and maintaining specific information about users. First-party cookies are those left on a computer by a Website that has been visited, while third-party cookies are those left by a domain different than the site being visited, such as an advertising server that has just delivered an ad to a computer, or certain third-party tools used to measure site traffic. Cookies are typically set to expire. There are two types of cookies: persistent cookies and session cookies. Session cookies are temporary and are erased when the browser exits. Persistent cookies remain on the user’s hard drive until the user erases them or until they expire.