AirDrop can be a convenient way to transfer files between iPhone and iPad. You activate AirDrop on your device from the Control Center. Tap on the AirDrop button and you will be prompted how you want your iOS device to be discovered.
It is advisable to setup your AirDrop to be discoverable by Contacts Only instead of Everyone. This limits your iPhone or iPad to be visible only from people on your Contacts. This will add a layer of privacy especially when you are in crowded public places or when you have a habit of turning on AirDrop all the time.
AirDrop requires both Wi-Fi and Bluetooth in order to work, thus it is a battery drain. The normal practice is to turn it on only when you need to use it.