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OSI Model
The OSI Model is a layered protocol model. It was proposed by the International Organization for Standardization. The model can be used as a reference to understand how networks operate.
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The model was created to have a standard which hardware/software producers could use so that different products could work with each other.
For example, before this model was introduced, hardware from company A could not work together with hardware of company B because the protocols and techniques used were completely different.
As you can see the model has 7 layers. Each layer has their own responsibility.
Note: We don't actually "use" the OSI model, we mostly use the TCP/IP Model now. The implementation is exactly the same, only some layers are different.
7. Application Layer
The application Layer provides services to the end user. So this is the layer the user actually interacts with.
These services are usually protocols that interact with the data that the user uses.
Examples of services (protocols):
- HTTP
- FTP
- IRC
- SSH
- DNS
- SMTP
For example a web browser like Google Chrome uses the HTTP protocol to browse files on the internet. And the mail client Outlook uses the SMTP protocol to send mail via the internet.