A Smartphone is a mobile computer (Mobile referring to being portable). Smartphones are all cellular devices that have an Operating System (OS). Most people associate Smartphones with touch screens. While this may be the case, some Feature Phones (phones with buttons) have Operating Systems which basically makes them Smartphones.
They are two major Operating Sytems in the Smartphone industry. iOS Operating System and Android Operating System. iOS Operating System was created by Apple and only used in Apple product such as iPhones and iPads. Android was created by Google and operates about 99% of Smartphones that are not made by Apple.
G in 3G stands for generation, with 3G standing for Third Generation of Mobile Data. 3G is the network that phased out 2G network system. 2G network allowed only the basic function of Smartphone capability but the introduction of 3G network allowed large Data formats to be accessible (standard HTML pages, music, and videos) and it was faster than the 2G network service.
Cheap 3G phones are Tecno Y2, Tecno WX3, Tecno WXP, Tecno WX4, Tecno W2, Fero A4001 Plus and Fero A5000 to name a few.