The letter G was created in the third centuryBC by Spurius Carvilius Ruga. At the time, the letter C sounded like the "c" in "cat" and the "g" in "girl". To make the difference more clear, Ruga created the letter G.
Letter G stands for GPRS (General Packet Radio Service). It indicates the slowest speed of Internet data transfer in your mobile phone. When you see G near your signal strength indicator, it is certain that your net connection is working at the slowest speed. 2G,3G and 4G indicates different speed of internet.