This document discusses the evolution of mobile phone technology from 0G to 3G. It begins by defining a mobile phone and describing the core functionality of 0G/1G mobile phones, which used analog signals and could only make calls. 2G introduced digital networks and SMS messaging. 2.5G networks added basic packet-switched data and higher speeds. 3G networks supported the first mobile internet and video calling, providing minimum download speeds of 0.2 Mbps. The document traces how each generation built upon the previous to add new capabilities and faster speeds.