Windows 10: What are environment variables in Windows and what does they do?

What are environment variables in Windows and what does they do? And why do we have to add an environment variable when we install any programming language in the PC?

:)

 

System environment variable won't stick

Running Win10 Home on an Acer Spin 3, 64bit, i7cpu. I try to add a path to the system environment variables by:

1. Control Panel > System > Advanced system settings > Advanced tab > Environment variables

2. The "Environment Variables" window opens.
3. In the "System Variables" pane I select "Path" and click the EDIT button.
4. A list of the current system paths is displayed.
5. I click the NEW button, browse to the path I want to add which is "C:\Python36-32" and click OK. The path "C:\Python36-32" is added to the list of current system paths.
6. I click OK and am returned to the "Environment Variables" window.
7. I click the "X" at the top right to close the "Environment Variables" window.

Now if I click the "Environment Variables" button again (end of step-1) and repeat steps 2-4, the new path I added in step-5 is gone. IOW, adding a new path won't stick.

What am I doing wrong?

 

Searching environment variable in list

I'm using a command that gives me a list of environment variables. When searching in the list, I want to find all environment variables with the word
EXTERNAL; using the following command all that is occurring is all the environment variables are being listed instead of those environment variables with the word
EXTERNAL ?

findstr /c "EXTERNAL"

 

System environment variable won't stick

Yes, there's an OK button for each step.