OSI model

OSI model stands for a open system interconnection model which was developed by apra net. It consist of severn layer.

Application Layer
Resentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer

You can have better understanding with the following infographics

1. Physical Layer: Physical layer deals with the actual connectivity between the source and destination. If you're transferring data to another machine through LAN, physical layer is the Ethernet connection. The water in the sea connecting your place and destination is the physical layer in our case.

2. Data Link layer: In this layer data is broken down into pieces. That is your goods will be separated in various categories, say expensive goods, fragile and non fragile. This layer deals with breaking the data being sent and transmitting it through the physical layer. So goods being categorized and sent through the sea.

3. Network layer: Here the data being sent is organized. It also decides which protocols to use, tcp or udp. So in our case the different compartments of ship where you'll keep these goods is the network layer. It will also decide which generators and engines to be used while travelling (protocols).

4. Transport Layer: Transport layer gives you the best route, security and safest path to the destination. The transportation of data takes place here. So think of the coast guard as transport layer. He'll look after the connection, inform you if there's any danger and tell you the best route to your destination.

5. Session layer: The best way to remember a session is thinking of it as a Hangout or Yahoo messenger chat. When two people start communicating a session is created, as soon as one ends the chat or disconnects session is broken. Session layer creates a new session for a pack of data. So the time when our ships leaves our docks and till the time it reaches the destination is one whole session, assuming there are no problems during that interval. If your ships gets hijacked by pirates, session is terminated. If the destination blows up, session is terminated.
Session plays an important role in online transactions. In the very last step, where you need to enter OTP or your secure password to authorize the transaction, if you sit idle for more than 2-3 minutes without any activity, the session will terminate itself and the transaction will be unsuccessful.

6. Presentation Layer: There are times you send various file formats through the network like images or videos. Presentation layer deals with all this different files. It converts this data into a readable format for the destination. Think of a captain who's in charge of people from various races, countries and languages. He has to make sure everyone will reach to destination and can perform their work over there.

7. Application layer: Many people think of browsers as soon as they hear application layer. But application layers isn't the browsers or application you're using. In our case if browsers are taken then ships will be out application layer.
But application layer is not the browser but the common protocols used by the browsers. So application layer are not the ships but the common fuels these ships are using.