Mass is the quantity of matter present in a body 

Weight is the gravitational pull of the planet on the body. It is the product of mass of the body and the gravitational pull of the planet. 

Mass remians same everywhere in the universe. its constant because the amount of matter contained in the object remains same wherever you take it. 

Whereas, weight depends upon the gravitational pull. The weight of an object becomes 6 times lesser on moon, as the gravitational pull of moon is 6 times lesser than Earth. 

If 'm' is the mass, 'g' is the acceleration due to gravity, then, 
Weight, W = m X g 

The value of g for earth = 9.8 m/s2 
If the mass of a stone is 2 kgs 
Then its weight, W = m X g i.e. 2 X 9.8 = 19.6 Newtons 

The units of Weight is given in Newton which is the unit for force, because Weight is also a force exerted by the planet on an object.

Hope this helps:)