The OSI Model

The Open Systems Interconnection model is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers
- Wikipedia

7 Application

Serves as the window for users and application processes to access the network services

6 Presentation

Formats the data to be presented to the Application layer, it can be viewed as the Translator for the network

5 Session

Allows session establishment between processes running on different stations

4 Transport

Ensures that messages are delivered error-free, in sequence, and with no losses or duplications

3 Network

Controls the operation of the subnet, deciding which physical path the data takes

2 Data Link

Provides error-free transfer of data frames from one node to another over the Physical layer

1 Physical

Concerned with the transmission and reception of the unstructured raw bit stream over the physical medium