End
As you have noticed, running a test opens a console-window showing the output of the webdriver that was launched – which will in turn launch the browser. In order to close the windows at the end of a test, it is recommended to call the End function which will close those windows and dispose all objects it created.
As the code uses NuGet, InitBrowser will create a temporary project folder for NuGet to work with which End will also delete. (If you do not call End in your tests, you may want to check the variable Selenium.myNuGetFolder and make sure the folder is deleted.)