Dear Mr. Nitin,
1) First of all you have get the idea "Why software application we need?" Ans:"To minimise the work load, and not in paper, you retrive the data when ever u need".
2) Where this application need? " Where ever the business is running (it can be any kind of transaction)"
3) Earlier mostly manfacturing induatries are there. They planned the operation through MRP.
( i.e): Material Resource planning. According to the material in stock, production are done. so application developed also based on MRP only.
4) After that business are attained globally. And every departement needs customisation and software application to compitate. so all come to the conclusion to focus on whole Enterprises. so they shifted their idea from MRP to ERP(Enterprises Resource planning).
5) Under ERP many software applications are developed
Eg:- Tally for accounts, People soft(HRM),oracle(Finance), IBM(CRM),SAP.
6) SAP is only company have developed all department application as each modules. and all these modules are interrelated. so if any changes in stores updates will be known by production department immdiately, same way marketing departement got any purchase order, immdiately it will reflect to inventory and production management and production departement too.
7) so HRMS is a Human resource managament system. its a entity. Application are developed for HRMS also...

SAP is the world leader in ERP packages...
9) Its having lot of department(modules), helps the business to run faster in this competition.
10) so i request you to work in HR departement and get the idea abt the core area, then do the SAP HR.
11) Mainly SAP is already developed, if u studied also, your work is customisation of that application according to your client need. so you have to have core knowledge about HR. then only you can win the race..
All the best.
Contact me for further queries.
With Warm Regards,
G.R.Vishaka Guru,
9894325508.