What do the different work order statuses mean?

Open ("O") is the initial state a work order receives when it is first created. Work orders are considered exploded ("E") once material requirements (and routings) have been generated for the order. Released ("R") is the status work orders reach when they have been released to the shop floor. Some actions—such as time clock entry—cannot be performed until a work order is released. Work orders are considered in-process ("I") once material requirements have been issued to the order. Closed ("C") is the final status reached when a work order is closed.