Cellular (4G) is a function found on the latest iPad that allows it to connect to Network using a data sim card, for data transmission. Unlike the wifi iPad, that allows transmission of data only in an area with wifi connection, the cellular iPad is able to allow internet connection wherever you are; on a motorway or even in a area with limited/no wifi connection. Cellular data can be provided using a 4G or 3G speed, depending on your preference. 4G is short for the fourth generation network type, which is about ten times faster than the previous third generation's network speed. Some customers assume because Cellular Ipad takes sim card, they believe that it can make and receive calls. This is not case with iPads as it is only design for data transmission but you can use apps such as skype , Viber and built in feature such as FaceTime to make call over internet connection.