Hi Bala,
In HR I don't have any idea But I will explain in Finance Area. Try to understand.
Development Server : For Customization Purpose ( All the creation work will done here )
Quality : For Testing Purpose
Production : Live Data. Finaly out put. ( End used will access )
Quality check only in Quality server only.
Development only in Development.
Production Live only.
Transport Req. means, For simple under stand its like a Folder. While developing we will save all the activities in the Folder ( Transport Req # ) and we will move the folder in Qc for testing if testing successful move to production for live.
Regards,
KVSSAPFIN