Hello Durga,

IT is the broad subject concerned with all aspects of managing and processing information, especially within a large organization or company. IT is generally not used in reference to personal or home computing and networking. While IT is often used to describe computers and computer networks, it actually includes all layers of all systems within an organization - from the physical hardware to the operating system, applications, database, storage, servers and more.

Some core subjects of IT are - 

Computer architecture and organization

Data Structures

Data Warehousing andData Mining

Database systems

Design and Analysis of Algorithms

Electronics

Engineering Mathematics

Foundations of Computer Systems

Java Programming and

Website Design Operating systems

Hope this helps.