One of Google+’s main components is Huddle. Huddle is a group messaging component that can essentially replace text messages for Google+ users. People who do not use Google+ can still be part of the message group via traditional text messages.
Google apparently thinks this feature is so important that they automatically install an app shortcut icon in the Android programs list. It is simply labeled “Huddle” and uses the g+ icon.
The second screenshot here shows the Google+ Android app’s Huddle interface. It looks much like a conventional smartphone text messaging app. But, it can do far more.