What is difference between conputer science and it?

They are used interchangeably by many organizations, mainly because most assume they are the same. There is only one true difference. Computer Science would deal more with processes while Information Technology with delivering information. See below...

Computer Science
the branch of engineering science that studies (with the aid of computers) computable processes and structures

Information Technology
the branch of engineering that deals with the use of computers and telecommunications to retrieve and store and transmit information