What is the difference between mass and weight of an object?

Weight is a force. Mass is the amount of matter a body contains.

The mass results in presenting the amount of substance or matter contained by a body. The weight is the force that is acted on the body by gravity.

These two are related by Newton's second law of motion, F=ma.

Force = Mass x acceleration. Acceleration is basically the gravitational pull by the earth, the value is a constant; 9.81 ms^-1.

So eg. my 'mass' is 58kg. We tend to say weight, because it is less scientific? :P I don't know, well anyways getting back so now we have two values, let's calculate my 'weight'.

F= 58 x 9.81 =>568.98 Newtons.

So the mass of an object will never change (unless you exercise or overeat and all) but the weight will, with respect to the gravitational pull of attraction.