IT is short for Information Technology and is pronounced as separate letters. Information technology is the broad subject concerned with all aspects of managing and processing information, especially within a large organization. IT is generally not used in reference to personal or home computing and networking.

I.T. is more than Computers and Networks:

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 systems, application, databases, storage, server and more. Telecommunication technologies and including internet are also part of an organization's IT infrastructure.

I.T. Departments:

Computer systems are central to information management, computer departments within companies and universities are often called IT departments.