Just like other browsers, Firebox private browsing used to work same way- it opened a new browser window right way that does not save the histories or cookie. But in this latest update, you can enable Tracking Protection while you are using Private Browsing mode.
Firefox version 42 can also block analytic trackers, different ad which contains embedded trackers, social share buttons or any parts of the website that may track your browsing activity. Basically it will make sure that your browsing behavior is not shared with any third party websites.
The latest version of Firefox has also gotten new Control Center which will allow you to turn on or off the tracking protection for specific site. Firefox VP Nick Nguyen wrote in a blog, ‘No other browser’s Private Browsing mode protects you the way Firefox does‘. In the official Mozilla blog, they have also published an introductory video which you can watch from below.
Few websites posted that Firefox finally announced it will be releasing an iOS app although the company refused to provide any details about this.