Relation between AR Invoice and Sales Order tables

Many times I have seen a question being asked in the forums about the relationship between AR Invoice and Sales Order.
There are several interface_line_attribute and interface_header_attribute columns in RA_CUSTOMER_TRX_ALL and RA_CUSTOMER_TRX_LINES_ALL table respectively which are used to map it with other modules.
The relationship is actually mapped using the descriptive flexfield.

Query for following
Application: Receivables
Title: Line Transaction Flexfield

and then in the context field is the listed different modules.

For Sales order search for Order Management or Order Entry and click on segments to see how they are mapped. Screenshots below

 

Click on the segments button to see column mappings.

 

The above method can also be used to find mapping of Receivables with other modules like Oracle Projects, Services, Contracts etc.

P.S. Please click on the image to zoom it.