Well... its one of hundreds of devices that claim to cause either insects or rodents to flee using a mixture of ultrasonic sound, smell from some form of natural or other perfume and (not in this one) heat and / CO2 (for insects).
I am not sure there is any firm evidence for any of it. It is even still up for debate as to what it is mosquitoes home in on. I believe CO2 is proven and body heat also. Not sure that any of the natural perfumes have been proven to be effective.+