got a mail from adsense Subject: AdSense Webinar: Increase Your Visibility To Advertisers Reply-To: Hello, We're excited to let you know that your account is one of a select few for which we've enabled a new feature called ad placements. Ad placements are groups of ad units that you can define and highlight to advertisers. Creating an ad placement is as easy as creating a custom channel, and ad placements will help you generate more revenue by increasing the visibility of your ad spaces to advertisers. For instructions on how to create ad placements, please visit https://www.google.com/adsense/support/bin/answer.py?answer=50691 . To help you learn more and take advantage of this new feature, we'd like to invite you to an AdSense webinar where members of the AdSense and AdWords Product Management Team will walk you through ad placements as well as provide you with valuable insight into what advertisers want to see from publishers. We'll also leave time for the team to answer any questions you may have on these topics. can anybody explain it ?