Pulling a 50 kg crate across a smooth floor is difficult because the mass of the crate is large, 50 kg.
If you tried to drag the box it across a floor on the Moon of the same type as the one on the Earth it will be just as difficult because the MASS of the box has not changed. It is still 50 kg.

Now imagine LIFTING the crate on the Earth. This time the important thing is the force of the Earth’s gravity on the crate. Lifting up the crate means that we have to move it against the force of the Earth’s gravity.

The gravitational attraction of the Earth is about 10 N/kg.

We call the force of attraction of the Earth’s gravity on an object the WEIGHT of the object on the Earth

The weight of an object is a force and is so is measured in Newtons, while the mass of an object is measured in kilograms.

To find the weight of an object on the Earth multiply its mass (in kilograms) by the force of the Earth’s gravity on 1 kg (10N).
On the Earth the weight of our crate will be 50x10 = 500 N

On the Moon the crate would still have a mass of 50 kg but because the Moon’s gravitational pull is only about 1/6 of the Earth’s (about 1.6 N/kg), the weight of our crate there will be 50x1.6 = 80 N and so it will be much easier to lift up.