Private browsing mode is a feature of the Firefox browser designed to not record the history of your web surfing. When you open a new private window, Firefox does not retain cookies, temporary internet files, history, and other data related to your browsing activities. When the Private browsing session window is closed, this data is cleared. Additionally, Firefox will reset the clipboard content for better privacy. Private Browsing mode can be activated in settings, there you can enable it permanently so Firefox always runs in private mode. However, you might want to run it usually in normal mode and only have a shortcut instead to run Firefox in private mode.