How scales work compared to balances?
In simple terms, the following can be said:
A balance is used to caluculate the mass of an object in comparison to a known weight.
A scale is used to measure the force exerted on a mass by the gravity of the earth, then to convert that measurement into a calculation of the object's mass.
Therefore, we actually measure mass, not weight.
A scale provides much more precise calculations than does a balance.