It effects it because everything is pushing down into the world, it is not like we are in space where everything just floats around, because if Earth was like space, we would always just be floating around and nothing would be able to stay in just one spot. That is where gravity comes in, the more mass it has the more heavier something will be, because all of Earths gravity is always pushing down on us. When an object is moving farther from Earth, it gets more and more lighter, because we are not on Earth anymore and gravity is not a thing in Space, it will just stay there and float like everything else that goes into Space. The Mass will change when we go into to Earth, it will not float around anymore, everything will just fall down because of Earths gravity and then the object will just become heavy.