Google+ Messenger and Google Talk, What are the differences between these two IM/Video Chat apps?

Google + is the social network, while Google talk is your basic GMail acct. For example, I have not signed up for Google +, but I have a GMail acct. The 2 are not interchangeable. And to talk on G+ your recipient also has to be signed up for G+.

I assume the G+ app is on your Gnex to drive people to the social network.

 

I guess Gtalk is connected in your gmail account it is there already, now if you talk about the Googlt+ I also believe that it's an application that is available the moment you signed in at your Google account. All of them are connected to each other which means all of them are interrelated to each other.

 

Google+ Messenger (formerly Google+ Huddle) is a part of the Google+ app, which is more meant to be a SMS-like service. Your conversations is always available on Google's servers, even though you decide to uninstall, and later reinstall the Google+ app again.
You can also share photos, and other content, through the Google+ Messenger service, to your other Google+ circlings.
When you receive a Message and / or incoming Hangout, then your smartphone will ring and vibrate just as normal calls and texts.

Google Talk has been around for many years now, and is the Instant Messenger (IM) service from Google, which is available for all platforms, both in the browser, and by installed software.

Both services support Hangouts, which is the webcam and / or voice calling part of Google.
Those Google Hangouts can both be public, for a specific circle, or private.
Google Hangouts has recently been very popular among many major TV-stations, celebrities (i.e. President Obama), organisations, companies, and others, where "normal" people can come and join the conversation.
A normal Hangout supports upto 9 participators at the same time, and some are streamed Live on Google+ and YouTube.

I hope that helped you understanding the differences, between Google+ Messenger and Google Talk.

 

Google+ Messenger is a Mobile Only Instant Messenging app which is available to Google+ users.

Google Talk is both a Mobile and Desktop (Browser) Instant Messenging app which is available to Gmail users..

They are currently separate because Gmail and Google+ users are NOT the same group of people, although they usually are.

Google+ is a Social Network, although it does NOT work like Facebook. It behaves more like a visually attractive Gmail.

Google+ Hangouts is a video conferencing function which can now be activated from within both Gmail/Google Talk and Google+/Messenger.

At a recent Google I/O, Google Inc. has promised to unify these services as soon as possible.

These services are the direct alternatives to Facebook/Facebook Chat/Facebook Messenger (mobile) and Microsoft/Skype (Text, Voice and Video Conferencing).

Google has acquired Gizmo5 and Meebo in the past, and might integrate these technologies into the upcoming, unified App. My understanding is that it will all streamline towards Google+/Messenger.

If I got anything incorrect, somebody please correct me. Thanks!