Is it '0' or is it equal to the product of the mass of the body and acceleration due to gravity? Please explain in relation to weightlessness of body in freefall.
Your weight always equals the gravitational force that is pulling in you. And it obviously pulls even when free falling. Otherwise, why would you fall at all?
On the ground this weight is counteracted by the normal force from the ground. What you are feeling is not your weight, but rather this normal force.
In free fall your weight causes you to speed up (accelerate). But you don't feel it because there is no other external force pushing up on you. (Except for maybe air drag...)
The reason that you don't feel your weight, the gravitational force pulling in you, is that it pulls equally in all parts of you. Think about what makes you feel a force: Your body and brain registers displacements of particles of your skin and limbs relative to each other as a sense of feeling or pain.
If you punch your finger into the wall so it breaks, then it only breaks and thus only hurts because the rest of your hand came from behind and squashed your finger after its motion was stopped by the wall. Had your hand been stopped as well exactly at the same time as your finger was stopped - meaning had they both felt the same exact force effect - then your finger wouldn't break and it wouldn't hurt. In fact you wouldn't even feel it.
So, in essense, the sense of feeling is the brain's interpretation of relative motion between parts/particles without your body which means different forces acting on different body parts or particles. When the same force acts on all parts and particles, then you don't feel anything. And that is why you don't feel gravity. That is why you don't feel any force while free-falling in outerspace. Because gravity is not causing relative motion between particles of your body.
Weight is the feeling of mass. And force which is due to mass is called gravitational force, while free fall a body experience gravitational force, which pulls it downward toward the centre of planet ( or any body, in this case earth). Weight is the gravitational force exerted by earth on the object. But you won't know how strongly earth is pulling you untill you get the equal and opposite force as that of earth( your weight).
Hence in free fall you can't feel your mass. But as soon as you hit the ground there is equal and opposite reaction force on you exerted by ground. And after reaching the ground you can feel your mass i.e how strongly earth is pulling you i.e your weight