This tab lets you specify which environment variables should be initialized on the service start and be accessible from within this service.
This is really useful for Java, Windows .Net framework and other applications that rely on custom environment.
To specify the environment variable, type or select its name, then type or select its value and click "Add" button:
Use "Delete" 
to delete the selected environment variable
… and "Up"/"Down" buttons 
to move the selected environment variable to the top/bottom.