The by-product of trimming is trim, AKA shake. This is the leaf matter and small pieces of flower removed during trimming that still contain THC and can be used in extraction, or in cases of exceptional quality, in pre-rolls or ready-to-roll products.
The quality (and thus ability to sell and the price sold) of trim is simply the ratio of flower to leaf matter. The more leaf, the lower THC and terpenes present. Sugar trim is very high quality that contains little or no fan leaf. Shake is more of a low-quality trim and typically contains a higher volume of leaf matter and even some stems.
If fan leaves are left on during harvest and are not removed prior to trimming, the quality of the trim will be very low. When fan leaves are removed, it is just the smaller leaves (sugar leaves) which are often coated in trichomes themselves, that remain. Then the quality of the trim is higher. Processing by hand is necessary to achieve the highest quality trim (albeit slowly), although an initial pass through a trim machine quickly to remove most of the leaves, discarding the trim, and then running material a second time will yield a very high-quality product. Storage parameters are identical to cannabis flowers.