You searched for a favorite topic using Google+ search and found interesting results that get shared by other G+ users. Looking at the results, you thought of sharing and discussing with your friends or circles.
Normally what you would do is, copy the link that appears on the browser, goto main stream and paste the link in the share box, add circles and share. Your circles will click on the link and see the same results as you (may see updated results if more content arrived during that time).
The good news is, you don’t have to do any of the above things. This is released as a feature in Google+ search.
Just search for your keyword as you would normally do and in the top of the search results you’ll find a new text box saying Join the discussion about “keyword” (refer image below)
Clicking on it and instantly share this topic with your friends or circles (Type in a message/thoughts and Add circles or individuals to the conversation)
This is a faster and quicker way of starting a discussion about any topic with your friends or circles in Google+.