Sandeep,
We can equate the HR department with the Production department and the Administration department with the Maintenance Department.
I will explain to you.
Maintenance Department: They normally carry out breakdown maintenance of machines, preventive maintenance, etc., and ensure the machineries in the shop floor are in working condition. This is the normal routine they do periodically.
Similarly, an administrative department or personnel department does the normal routines like payroll processing, statutory compliance (like submitting periodical returns), time office functions, etc. These are monotonous and regular jobs.
Production Department: As you may know, in the production job, there is INPUT -> PROCESS -> OUTPUT. The raw materials are put into one side of the system, processed in different machines (drilling, turning, thread cutting, machining, grinding, boring, etc.), then come out as an output after the quality check, to be delivered to customers, is it not?
Similarly, an HR department's product is nothing but an employee himself. The HR department hires a person, inducts him, teaches him the system and procedures, puts him onto the job, molds him to requirements, finds strengths and weaknesses (by the performance review system), provides him necessary training/ retraining, plans career development, and finally makes him available to the organization/department as a competent person.
It is developing an ordinary individual into an extraordinary employee to be used by the organization for its business.
Therefore, the HR department is usually known as the "HRD department" - Human Resource DEVELOPMENT Department.
Hope I have clarified your doubt.
V. Balaji