According to new information that was posted to 4pda.ru, Windows Phone “Apollo” will bring platform parity with Windows 8. We must stress that this new information has not been confirmed but does align to previously rumored information.
If you are asking what platform parity means, according to the source, this means that the phones OS is now based on the NT kernel where as it was previously based on the Windows CE kernel. The key here is that Windows Phone Apollo will use the same core system from Windows 8 which means that it is a minimal Windows system that boots, manages the hardware/resources, authentication and can be managed at a basic level.
The source also states that all desktop binary images must be signed with a trusted Microsoft certificate;
WOA platforms will require that all desktop binary images be signed with a trusted Microsoft certificate. Any unsigned code will fail to load ... This ... does not cover Metro Style applications for which there is a separately documented signing requirement and developer licensing
The final major change is the adoption of the ESENT platform, as stated below:
The final significant changes of note are the adoption of ESENT, also known as Jet, for the database engine, and the managed-code runtime. Rather than using the .NET Compact Framework from Windows Phone 7, Windows Phone ”Apollo” uses the Core CLR produced by the Developer Division at Microsoft."
All of these changes will help to bring the Windows Phone platform closer to that of the desktop experience. While no indication has been leaked about when the new update will be released, it shows the direction that the platform is heading.
The individual who posted the information also created another topic with the entire document according to another source, but that topic was quickly deleted as the individual feared it could track back to him.
Thanks to Roman for the tip!