input: [Cookie Name] Google User Tracking PREF [Purpose] 
output: Set by a number of Google services and libraries to store any user-preferences and to track users from site to site. As this cookie is set by a third party system it is impossible for us to specify under exactly which conditions it is set, but it appears to be set when the user views a page containing any one of a number of Google services (including ReCAPTCHA, embedded Google Maps and the like), and expires after two years.