A much awaited capability to have "Pending Changes" window outside of the Team Explorer, like what we had in VS 2010, is added by MS in TFS 2013 Team Explorer (and in VS 2013). This will be a very good news for the developers who did not like the pending changes inside team explorer in VS 2012. (Including me as a matter of fact).
Cool thing about this is anybody who wants "Pending Changes" inside Team explorer, like in VS 2012, still can have it. People like me can switch it to a separate window.
Let me show you how to do this "Undock" of "Pending Changes" window from team explorer.
1. You can get "Pending Changes" window inside Team Explorer by clicking Pending Changes in Team Explorer Home.
2. Click on the top right hand side arrow as shown below.
3. There you go... now your Pending Changes appear as a separate window, you can dock it in VS as you like and unpin,pin works as all other windows.
4. If you hide it it will appear in the position you dock it in VS. You have the option to dock it back in Team Explorer by clicking the menu option or by closing the Pending Changes window.
5. Same behavior exists for Build explorer window as well.