In process inventory includes the products you are manufacturing but they are still in a phase of production that is, they are incomplete. At any given time some of you inventory will be in the process of manufacturing and is called in process inventory. Safety stock is the stock of finished goods you keep in hand above your normal inventory level in case the demand exceeds supply. You can meet this excess demand with safety stock. It is basically the extra units in stock. Seasonal stock is when you build up inventory because you think that there mat be a surge in demand during a particular season like Christmas.
