An open system is a model which allows any two distinct systems to communicate regardless of their underlying architecture. The reason of the OSI model is to open communication among different devices without needing changes to the logic of the underlying hardware & software.
The OSI model is not a protocol, this is a model for understanding & designing a network architecture which is inter- operable, flexible & robust.
The OSI model has a seven-layered architecture. These are described as:
Application layer
Presentation layer
Session layer
Transport Layer
Network layer
Data link layer
Physical Layer