More or less it redistributes the moisture evenly and allows the bud to continue drying slowly. Is it necessary, no but its like aging alcohol or tobacco you don't need to but it will be much better if you do. As far as how to do it, after you have let your bud hang dry then you put it in a jar, close the lid and only open the jar X amount of hours a day then close it back up. More or less. Hope this helps.