As the name suggests it can do the job of the flaps and ailerons. It can be both controlled differentially and symmetrically. If the pilot gives it a roll command one flaperon will go up and the other will go down, giving a rolling moment due to the difference in lift in both the wing surfaces.
When the pilot controls it by the flap lever, both flaperons will move down functioning like any other flap surface, giving a higher wing camber increasing the wing’s capability to produce lift at low speeds.
The mixer unit combines both these commands (flap and aileron) when pilot operates them simultaneously and change the flaperon suitably . It reduces the mass of the airplane as you would not require a separate aileron and flap system. V22 Osprey uses flaperons.
In large commercial airplanes, it helps to roll the aircraft more efficiently. They do however have flaps and ailerons as well. So, there is no major mass advantage here.
Source : Quora