Answer Description
Airplane mode will disable any cellular transmission functionality and will keep the phone from using any data or services while in a foreign country. Some devices now allow WiFi in airplane mode, but this will depend on the device and OS version.
Wikipedia
Airplane mode, aeroplane mode, flight mode, offline mode, or standalone mode is a setting available on many smartphones, portable computers, and other electronic devices that, when activated, suspends radio-frequency signal transmission by the device, thereby disabling Bluetooth, telephony, and Wi-Fi. GPS may or may not be disabled, because it does not involve transmitting radio waves.
The name comes from the prohibition by many airlines of using equipment transmitting radio-frequency signal while in flight; using airplane mode …
Airplane mode - Wikipedia, the free encyclopedia