Invoke a Command-line Program Using Python
In Windows, Linux, MacOS, etc. you can either start up programs using the user interface (pointing and clicking with your mouse) or from a command line. When you run something from the command line, it does basically the same thing behind the scenes, but you type commands instead.
For example, in Windows, you can open Internet Explorer, by going to the Start menu, going to All Programs, and clicking on Internet Explorer. To do this from the command prompt, you could go to the Start menu, click on Run…, enter cmd (which brings up the command prompt, and then enter iexplore.exe (assuming Windows is configured correctly for this).
This is just a toy example, but if you wanted to do the same thing from Python you would use this syntax:
import os os.system("iexplore.exe")
In practice you would probably never invoke Internet Explorer from Python, but it gives you a lot of flexibility to invoke whatever programs, written in whatever languages, that you want.