In tems of the Demand Characteristics, there are two types of demand: a demand occurs individually, and a demand is required depending on another demand. The former is Independent Demand, and the latter is called Dependent Demand. 

The Independent Demand occurs by the request of customers for products, kit products, service parts. This demand also individually and independently happens for each item, and has no relationship with other items. Thus it is used as it is to setup the production plan. In addition, the item to be independently demanded is called Independent Demand Item, which is usually used for production planning and is not used for MRP.