Collective intelligence is the collaboration and contribution of different minds, perspectives, and knowledge on the one idea.
An example of collective intelligence could be Wikipedia; where users accumulate their intelligence on a particular subject, and from there ‘gatekeepers’ come into play, to edit the users information.
An argued site of collective intelligence could be Facebook, users comment and like uploaded material, being the subject. Users form their opinion on the subject. I would argue that Facebook isn’t intended as a collective intelligence site, but factors such as commenting, contribute as collective intelligence.
These ideas are discussed in the linked podcast by myself (emma congdon) and Paige Whitfield.