Geolocation is a means to discovering the physical location (in real-world geographic terms) of an object.
Geolocating has become so prevalent that the W3C published its own Geolocation API in HTML5, allowing phone owners to share their location(s) between web sites that they trust. The hosted device's lat and lon are provided to JavaScript on the document, which can then be used for geolocation.
It is extremely important to clarify that HTML5 Geolocation can possibly compromise the user's privacy and therefore is explicitly turned off by default, and must be enabled by the user.
References:
http://dev.w3.org/geo/api/spec-source.html
http://diveintohtml5.info/geolocation.html
