What is the differrences between Talk and Google+ Messenger? Both are the chatting tools of Google.

I use Talk since I use Gmail to chat with my friend and when I see Google+ Messenger, I just thought it is Talk but the two are NOT the same at all - i.e. chatting with one person on Talk  and he/she will NOT receive it Google+ Messenger.

This is so confusing. What is the differences then? Why there are two chat tools like this?

Update
The funny thing is that Google+ Messenger is used for chatting with Google+ users from Android phone. But when I log in my Google+ page, I can ONLY talk with Talk friends !?!? I want to continue my last chat with a friend on Google+ from my PC, but now I cannot. So funny!
Google Talk syncs to your Gmail account. This offers free instant messaging to all your Google contacts that you have invited to “talk” with. You can use the services within the Gmail web page, or download Google Talk and install it on your computer or smart phone.

Google+ Messenger, originally called “Huddle”, is a sub service to Google+.

The big difference between the two is that Google+ Messenger is the instant messaging service that is synced to your Google+ account, not your Gmail account. People who are added to your “circles” are the ones that are able to be messaged with. Another difference is that Google+ Messenger allows people to have group chats.

Source: difference-between-google-talk-google-messenger-and-google-hangouts