C.G.[center of gravity] is the location on the wing where the plane balances front to rear. The best location for this is not a specific point but rather a range. Moving the C.G. to the rear makes the plane more responsive to control inputs and less stable. As a general rule the range will be between 25%-32% of the wing cord, or mean aerodynamic chord {MAC} on a tapered wing. For instance if your wing is 12-inches from front to back the C.G. would be 3-4-inches back from the leading edge of the wing.