Data roaming is the term used, when you are using data on a mobile network that is abroad (or in another area). Roaming is not typically included in your standard cell phone plan, and roaming rates are typically much higher than what is included in monthly cell phone service. In many cases roaming charges can be incurred by simply leaving your phone turned on when it moves outside your home network (in most cases your country). Some mobile applications may automatically send and receive data even in if they are not in use be sure to check your setting so that you don't incur fees without intending to. Before traveling be sure to investigate the roaming rates, check to see the additional service charges that are incurred when outside of your service area.
International data roaming charges can be expensive. Consider using your cell phone in airplane mode and connecting to Wi-Fi hot spots for any "data exchanges", you will not be able to send or receive text messages or phone calls on the Wi-Fi, but in most cases you can use the Internet, messaging apps and check email using the Wi-Fi Connection without incurring any data roaming fees.
