Developed by the International Organization for Standardization (ISO), the OSI model divides the functions of a networking system into seven distinct layers. Each layer serves a specific function and communicates with the layers directly above and below it.

Layer 1 - Physical Layer:

• Handles the physical connection between devices and the transmission of raw data bits over the physical medium (like cables, fiber optics, etc.).

• Examples include Ethernet (cable) and Wi-Fi (wireless).
  

Layer 2 - Data Link Layer:

• Responsible for node-to-node data transfer and error detection and correction in the physical layer.

• Divided into two sub-layers: Logical Link Control (LLC) and Media Access Control (MAC).

• Examples include Ethernet, PPP (Point-to-Point Protocol).
  

Layer 3 - Network Layer:

• Manages packet routing through logical addressing and path selection (IP addresses are part of this layer).

• Examples include IP (Internet Protocol), ICMP (Internet Control Message Protocol).
  

Layer 4 - Transport Layer:

• Ensures complete data transfer and data integrity between host-to-host (end-to-end) connections.

• Manages flow control, error checking, and segmentation/reassembly of data.

• Examples include TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).
  

Layer 5 - Session Layer:

• Manages sessions between network applications, establishing, managing, and terminating connections between end-user applications.

• Examples include NetBIOS and RPC (Remote Procedure Call).
  

Layer 6 - Presentation Layer:

• Translates data between the network and the application layer, ensuring the data is in a usable format.

• Handles data encryption, compression, and translation.

• Examples include SSL/TLS (Secure Sockets Layer/Transport Layer Security), MIME (Multipurpose Internet Mail Extensions).
  

Layer 7 - Application Layer:

• The closest layer to the end-user, interacting with software applications that implement a communicating component.

• Examples include HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol).

Understanding the OSI model is crucial for network professionals as it provides a universal language to describe networking functions and capabilities. It aids in diagnosing and resolving network problems and in designing and implementing new network solutions.