This is a bracket poll set up as a series of 1-on-1 match ups. Users are presented with the match ups and vote their choices, and these votes are tallied with votes from all the other users. The choices in each match up with the most votes are the winners and advance to the next round, until a final winner is reached. (If you vote for a choice but that choice did not receive the most votes overall from all users, then it will not show up in the next round.)
One key difference from a normal bracket poll is that this one has no end date and the user can vote in all the rounds in one session, right to the final winner. The winners are based on all votes received up to that moment and may change as more votes are received over time.