If you click on Gmail's "Help" link at the top of the page, you'll be sent to an appropriate section from the Gmail Help Center. Instead of always linking to the help center's homepage, Gmail links to the priority inbox section if you're using Gmail's smarter inbox, it shows the articles about filters if you're trying to create a filter and the articles about contacts if you're using Gmail's contact manager.
It's a small change that makes it easy to find useful information about the Gmail feature you're currently without having to type a query. Hopefully, Google will add this feature to other services, just like
the interactive bug reporting tool, which is now available in Gmail, YouTube and AdSense.