False alarm is when you after a period of stabile operation get alarms without any appearent reason. When you get a false alarm, the video or images clips received show no motion and sound. The camera should not be sending video/images if there’s no motion or sound, so it means the camera has stopped operating properly. Most IP cameras today work without problems for months, but will at some time need to be restarted. The cure is normally to power off-on and the detection will work again.
Also see What should my camera settings be?