Push requires more power and may have an effect on battery life.
Fetch New Data is a feature that allows the user to select how often the device checks for new data. Push is a feature that's only available with certain accounts that automatically push data to the device.
The steps below apply to the following models:
iPhone X / XS / XS Max / XR
iPhone 8 / 8 Plus
iPhone 7 / 7 Plus
iPhone 6 / 6 Plus / 6s / 6s Plus
For other models, click the applicable link for instructions: