Hi Venkata,
As stated by Mr.Aditya PS is the module which integrates with most of the modules like SD,FI,CO,MM,PP,QM,PM,CS,HR
SD : Milestone Billing, Gets updates from PS for activity confirmations, DIP profile linking. Account assignment[WBS] gives the planned revenue.
FI/CO : Accounting posting against WBS and Activity. Which gives planned actuals through controlling documents.
PP: Production against WBS. Cost goes to the project.
QM : Approving/Rejecting materials marked for quality inspection and capturing the cost of it.
PM : Preventive/Breakdown orders and the cost of the same to Project.
HR : Timesheet updates
CS : Customer service[After Sales Service] and capturing the cost the project.
MM : Procurement against WBS
Regards,
Senthil Venugopal