The TCP/IP model or Internet reference model, sometimes called the DoD model (DoD, Department of Defense), is a layered abstract description for communications and computer network protocol design. The structure of the Internet is still closely reflected by the TCP/IP model.

The Open Systems Interconnection Basic Reference Model is a layered, abstract description for communications and computer network protocol design, developed as part of Open Systems Interconnection initiative. It is also called the OSI seven layer model.

The TCP/IP has fewer, less rigidly defined layers than the commonly referenced OSI model, and thus provides an easier fit for real-world protocols. The two can roughly be related but are not a perfect match. The first striking difference is the layer count. The TCP/IP model uses four or five layers while the OSI model uses seven.

The three top layers in the OSI model - the application layer, the presentation layer and the session layer - are lumped into one layer in the TCP/IP model. The reason is that, although the functionality of these layers may be supported by TCP/IP protocol suite, these layers do not exist as separate processes with standardized Application Programming Interfaces (APIs).

Here you can read more about the two models: [1] [2] [3]