Everyone knows about Google +, Google’s social network, but the old Google + was the use of the + sign in the Google search box for exact matching on your keyword searches.

Google described this operator on their Google search operator help page as:

Google recently removed this from the page and no longer supports this special operator.

There are some complaints in the Google Web Search Help forums, in which Kelly F. from Google replied that you can still get the same results with the quote operator. She explained:

Are you sad to see one of Google’s oldest search operators go away? Do you suspect it has to do with confusion around Google +, the social network?

Forum discussion at Google Web Search Help.