Microsoft will introduce its new browser with Windows 10 on 29th July 2015 and has confirmed it will be the default browser in all versions of Windows 10
IE11 will still be available in Windows 10 for compatibility and other reasons
Microsoft has confirmed a number of plug ins including Silverlight and Flash will not be supported in Edge as they are placing a greater emphasis on security with their new browser
There will be no support for VML, VB Script, Toolbars, BHOs or ActiveX
See Microsoft's post on the reasons for the changes and how they intend to make the browser more secure