Mobile data (cellular data/mobile data) and have mobile Internet on your iPhone. If disabled, it will not happen to survey the Internet and use applications that need Internet connection. Apps like email or calendar, even when off the Internet may provide some functionality, but for their complete operation of mobile data is needed.
It is worth noting that disabling cellular data on the IPhone doesn't mean that you won't be able to come up with a device to the Internet. There is still Wi-Fi, and mobile data you can always turn it back on.
3G is the speed of your mobile Internet. If you have an iPhone there is a possibility, then just disable 3G back to 2G. Off the 3G in this case helps to extend the battery life, thus you can continue to use GRPS and EDGE (slower Internet standards).
The data roaming (data roaming/data roaming) is the use of mobile Internet abroad. Sometimes the operator takes a lot of money for the use of mobile Internet, so when abroad it makes sense to turn off iPhone data roaming.
Now let's look at how to disable the iPhone to the Internet - be it mobile data or 3G data roaming. For example, take iOS 6, other versions of the settings are slightly different, but not so much that it was impossible to navigate.
First go to your phone's settings, select the "Main/General", then "Network/Network". Use the slider to disable 3G or cellular data. This menu item is disabled and data roaming. If you want to return the Internet to your IPhone, then just take the opposite effect by scrolling the slider to enable the required functions.
You can scroll through this menu below, there you will see a set of settings to limit the transmission of cell data from different applications. Certain applications issue warning messages that their use of mobile Internet can get expensive, but before you start, not all applications and notify!