Recalibration in The Division 2 is a means of tweaking your existing kit to gaurentee them a particular attribute. Effectively, you take from one item, and put a part of it onto another. With weapons and armor having a variety of bonuses, min-maxing in this fashion is fundamental in ensuring your gear-score is kept at its height, and your bonuses synergize effectively. Below is an infographic pulled together by Voidlust, that lets you know all about Recalibration.