The same image is shown to a lot of people. If a majority of people click on the same things, that is assumed to be the correct answer. And it is added to the training database. Occasionally you’ll get one that hasn’t been shown to enough people yet to know for sure. For those, they’ll usually accept any answer, even wildly incorrect ones. The thing is, you as a user never know which ones they already know and which they don’t.

Wrong in the sense that the machine thinks it is right (or enough people disagreed with your judgement).