"OSI stands for Open System Interconnection. It is a reference model that defines how applications communicate with each other over a network. There are seven layers in the model, and each has a specific function. These are:

Physical - How data is transmitted and received through a network medium. Ethernet is an example of this.
Data Link - Defines the error-free transfer of data between network nodes using encoding and decoding.
Network - This layer chooses the physical path that should be taken by the data based on how the network is performing.
Transport - Keeps the messages in sequence, without any loss or replication, resending the data if necessary.
Session - Establishes a session or connection between the processes used by each node, then terminates it.
Presentation - Also known as the syntax layer, formats the data and presents it to the application layer.
Application - Mediates between the users and the applications, providing services such as email and file access."