Hi Radhamadhab, If you want to know about Google+, Ankit has given the proper link, which will help you to understand google+ easily. But if you want to know how to earn through Google+, then sorry Google+ by now has no such options which will help anyone to earn through this site. It is just like Facebook a social networking site.
But in future there huge possibility that one can earn through Google+, by monetizing your blog and associating the blog with Google+.
So keep tune with this platform and we will keep informing you about any such happenings.
And I am sure you can earn a good amount of money through that site(Google+).