What does scheduling do?

Scheduling on order management 

1. Determines source (warehouse) for the sales order line based on the sourcing rules
2.It derives Schedule ship date, Schedule arrival date,  Delivery lead time and Shipping method.
3. Scheduling also set the VISIBLE_DEMAND_FLAG to Yes and makes order line visible to the planning applications .

We can schedule the line automatically by setting either of below options 

1. Setting Profile option - OM:AutoSchedule
2. Set the Autoscheduling check box while defining the Order Transaction type.
3. From Order UI , Sales order line Tools > Autoschedule.
4.Set scheduling Manually by 
Right click the line and then Select  progress Order.
Run Concurrent Program "Schedule Orders".
Use workflow to schedule line.
Select the Order line then Tools > Scheduling from Sales Order form