A mobile phone or mobile also called cell phone and hand phone, as well as cell phone, cellular phone, cell, wireless phone, cellular telephone, mobile telephone or cell telephone is a long-range, electronic device used for mobile voice or data communication over a network of specialized base stations known as cell sites. In addition to the standard voice function of a mobile phone, telephone, current mobile phones may support many additional services, and accessories, such as SMS for text messaging, email, packet switching for access to the Internet, gaming, Bluetooth, infrared, camera with video recorder and MMS for sending and receiving photos and video, MP3 player, radio and GPS. Most current mobile phones connect to a cellular network of base stations (cell sites), which is in turn interconnected to the public switched telephone network (PSTN) (the exception is satellite phones).
The International Telecommunication Union estimated that mobile cellular subscriptions worldwide would reach approximately 4.1 billion by the end of 2008 and mobile phones are starting to reach the bottom of the economic pyramid. A mobile phone proper typically has a telephone keypad; more advanced devices have a separate key for each letter. Some mobile phones have a touch screen.