corner weighting is where you have the car weighed at all 4 corners, this lets you know how much weight is resting on each wheel
you normally want to take measurements with the driver in the car too
basically you adjust spring height or perch on each corner until you have an even weight distribution from side to side on both axles and then you can adjust weight distributiion from front to rear
on my EK9 there is only 30lbs difference between the sides front AND rear, because it was SO close for a road car i didn't both adjusting although i did lower the back more to get the car sitting level all round, the nose down stance it had before didn't do much for handling, felt like the back end was a bit perched through corners, feels much flatter now. i've gone for a 60/40% weight distribution front/rear which is fairly normal for a FWD car
having this done makes sure that you keep the car in balance