NEWNYM (as used by Vidalia’s “new identity” button) prevents hidden service-related activity from being linkable. It provides more information to Vidalia so you can see if your bridge is working. 0.2.25-alpha revamps the Entry/Exit/ExcludeNodes and StrictNodes configuration options to make them more reliable, more understandable, and more regularly applied. If you use those options, please see the revised documentation for them in the manual page.
Source: https://thehackernews.com/2011/05/tor-02225-alpha-released-to-toggle-or.html