MRP is shorthand for materials requirements planning. Big Business offers simple planning functions so you can see how your orders may need you to build more kits, and your kits may need you to buy components or wait for components on order.
Show Allocated brings up a list of orders, including kits, that need the item you are looking at. In our example, Bike and Bike2 both need BikeWheels, which are a subassembly that needs BikeSpokes. Big Business tells you how many and when.