Dear Shashikant,
What is EBP? SAP Enterprise Buyer Professional. Simply put, this is the central component of SRM to integrate a typical procurement process with the Internet.
What is SUS? Supplier Self Service. SRM component to enable Suppliers to collaborate with the procurement organization.
http://wiki.scn.sap.com/wiki/display/SRM/Supplier+Self+Service+and+Registration
SAP recommends separate clients for purchasing application (EBP) and Supplier Application (SUS). Please refer SAP note 573383 for more details.
Follow-on documents are all the documents you might create based on a Shopping cart or RFx in SRM. Whether SRM or ECC creates these documents depends on your so called "Technical scenario".
Check out here what are the different technical scenarios and how follow-on docs are created:
http://wiki.scn.sap.com/wiki/display/SRM/Shopping+cart
On top of what you see here, if you are new with SRM, please take the time to go through the SRM Wiki and SRM on SAP Help:
http://wiki.scn.sap.com/wiki/display/SRM/SAP+SRM
SAP Supplier Relationship Management (SAP SRM) – SAP Help Portal Page
Hope I was able to help you 
Imre