Computer telephony integration, also called computer–telephone integration or CTI, is a common name for any technology that allows interactions on a telephone and a computer to be integrated or coordinated. The term is predominantly used to describe desktop-based interaction for helping users be more efficient, though it can also refer to server-based functionality such as automatic call routing.For Salesforce CTI integration, kindly visit the below URL

http://login.salesforce.com/help/doc/en/salesforce_cti_developer_guide.pdf