IP Geolocation is a technique to identify the subject party's IP address, then determines what country, state, city, ZIP Code, organization, or location the IP address has been assigned to. There are several IP geolocation providers in the industry supplying IP address databases. These databases contain IP address data which may be used in firewalls, domain name server, ad servers, routing, mail systems, web sites, and other automated systems where geolocation may be useful. You can visit IP2Location.com for a free demo.
W3C Geolocation API is an effort by the World Wide Web Consortium (W3C) to standardize an interface to retrieve the geographical location information for a client-side device. The most common sources of location information are IP address, Wi-Fi and Bluetooth MAC address, radio-frequency identification (RFID), Wi-Fi connection location, or device Global Positioning System (GPS) and GSM/CDMA cell IDs. The location is returned with a given accuracy depending on the best location information source available.
Geocoding is often related to Geolocation. It is a process of finding associated geographic coordinates (latitude and longitude) from other geographic data such as city or address. With geographic coordinates the features can be mapped and entered into Geographic Information Systems. Reverse geocoding is the finding an associated textual location such as an address, from geographic coordinates. You can visit GeoDataSource.com for a comprehensive list of world cities with latitude and longitude.