Google Moderator is a tool that allows distributed communities to submit and vote on questions for talks, presentations and events.
From its Wikipedia entry (as of 1/29/17):
The service allowed the management of feedback from a large number of people, who could vote for questions they thought should be posed from a pool of questions submitted by others or submit their own to be asked and voted on. The service aimed to ensure that every question was considered, let the audience see others’ questions, and helped the moderator of a team or event address the questions that the audience most cared about.
Google Moderator was shut down on June 30, 2015 because the usage did not match Google’s expectations. The site remained available as read-only until August 15, 2015, at which time it closed completely. Content will remain available for a minimum of two years via Google’s Takeout tool. Since the shutdown, the term has been used to refer to Google Moderators, an advanced permission given to certain accounts to allow the user to monitor certain aspects of Google and take administrative action(s) when needed.
Some remaining alternatives (in alphabetical order) to Google Moderator are Kiunei, Loomio, Mentimeter, Pigeonhole Live, Poll Everywhere, and Sli.do.
Information on how Google Moderator worked can be found here.