In order fulfillment, there is a cost to assembling every order that comes in, according to how many products are in that order (usually). Kitting is when you pre-assemble individual items into ready to ship kits. This saves everyone time and saves your company money. Kitting is a great option if you have a top selling order (e.g. your 3 most popular items or a new client gift package) that you ship regularly. Having your order fulfillment provider kit them upfront will save you money in the long-haul.