This is an acronym for Transmission Control Protocol / Internet Protocol. This is a collection of applications, protocols and services. TCP/IP protocol was developed prior to the OSI model thus its layers do not match with the OSI model.
The TCP/IP protocol suit is built of the five layers: Physical layer, data link layer, network layer, transport layer & application layer. The initial four layers provide physical standards network interface, internetworking & transport mechanism while the last layer includes the functionalities of the three topmost layers in the OSI model.