Failsafe means fail-safe. This is the drone's coming home facility, i.e. a kind of protective mechanism. The drone saves its starting point via the GPS and can be brought back there at the touch of a button on the transmitter if required. If the transmitter signal fails unexpectedly, for example, the drone automatically returns to the take-off point and lands on its own. This function prevents the copter from getting lost or moving uncontrollably in the airspace.
If you would like to find out more about the failsafe, take a look at Youtube:
