Weight is often confused with mass. Weight (W) is the force on a body due to its mass and is given by Newton's second law of motion as the product of mass of body (m) and acceleration due to gravity (g).
W = m x g
The units of weight are the same as those used for force, i.e. Newtons (or N) in SI system or, kg.m/s^2. In the FPS (foot-pound-second) system, the units of force are lbs (pounds).
An interesting aspect of weight is that it is not constant unlike mass of a body. If we move to another celestial body, with a different acceleration due to gravity, our weight will change (although the mass will remain the same). For example, the value of 'g' on moon is about 1/6th of its value on Earth. Hence the weight of same body would be one-sixth of its weight on Earth.
Hope this helps.