Types of Servers/Environment

Production Server

It is a server which is accessed by the end users or the real users and it contains the real time data of the end users.
The application or the software is installed into the production environment once it is developed, tested and working according to the customers requirement, the modifications and testing should not be done directly on production environment as the data is secure and it is accessed by the real users. Hence production server is also known as Real server or Live server.

Development Server

It is the server which is accessed by the developers for writing the code as well as for doing bug fixes.

Test Server

It is the server used by test engineers for testing the application or software.
We should handover the bugs to the developers as soon as we get it so that developers get enough time to analyse and fix the bug.

The developers and test engineers will have separate environment/server so that both of them simultaneously can proceed with their work.

Staging Server/Pre-Production server

It is the server which is accessed by test engineers, in pre-production server the test environment is kept similar to production environment.
In pre-prod server the test engineer do the system testing i.e, do end to end testing as before doing system testing if we installed the software in the production server than the application might not work because the test server and development server configuration is less and production server is highly configured, so for doing system testing we create a server similar to the production server and due to this in system testing the test environment is similar to production environment.

Why Testing Environment is similar to Production?

Since, if the application is tested on smaller environment and directly move to the production, we may face some issues to avoid such issues we should maintain testing on environment similar to production environment.