How to find Descriptive FlexFileds Segments defined for paticular Application
For Example if you want to know the Descriptive Flexfields defined for your Purchase Requisition Header level form,
Go to System Adminstrator Responsibility--->Application--->Flexfield--->Descriptive--->Segments--->
Here you can give F11 and query for Application 'Purchasing' and Title as 'Requisition Headers'
and here you can see how the segments attributes are defined.