What is the meaning of calf pre-weaning?

Calves are trained to eat out of a feed bunk (called getting "bunk-broke") and a water trough, and are also vaccinated, dehorned, tagged, castrated (the last three are optional if they haven't been done a few months earlier) and dewormed prior to being weaned. This is a method that is being caught on by a lot of cattle producers because it decreases stress for the calves at weaning time; all these calves have to complain about is being away from their mothers, without having to undergo more stress and pain from having to be ran through the chute all in the same day.