If Google+ is enabled on your domain and you activated your profile, the following features will now be available in your Gmail account:

– Circles and Google+ posts in the People Widget: If you open an email from someone that has a Google+ account, you can add them to a circle. The People Widget will also show recent Google+ posts from the sender.

– Direct content sharing: If you receive an email with an image attached, in addition to viewing or downloading, you can now share it to Google+, directly from your inbox. The photos will be uploaded to your Google+ account and will only be viewable by circles you choose to share with.

– Filtering mail by circles: Your circles will be displayed as labels in the navigation pane. By selecting a circle, you can choose to display messages received from individuals in that particular circle. Additionally, you can configure circle names to display on emails in your inbox.

How to access what’s new:
-To hide your circles from the list of labels, select the downward arrow next to Circles, and then choose ‘hide’.
-You can enable or disable circles displaying on emails by selecting the gear icon, Settings, Labels, and then choosing either ‘show’ or hide’ under the ‘Show in message list’ pane.

For more information:
http://gmailblog.blogspot.com/2011/12/gmail-and-contacts-get-better-with.html