Therefore it is a COM or "Center of Mass".
Strangely enough, aircraft performance data specifies "centre of gravity", not centre of mass and that CG datum becomes very important to safe and legal flying.
Time to put this erudite stuff to bed, pass the exams, get a license and then learn to fly, where I can assure you that you won't be too worried about the difference mass or weight, when you are flying around on a glorious VMC day with bandits in all sectors.
By the way, just so it does not come as a terrible shock, when you set the flaps to 25 degrees, it isn't really 25 degrees, its just an approximation, like the stuff you need to know to pass your exams.