The voters’ choices are counted until there is a candidate with more than 50% of the votes. First choices are counted first, and if a candidate has 50% of the votes or more, they’re the winner. If there’s no candidate with 50% or more, the candidate with the lowest number of votes is eliminated and everyone who voted for them has their second choice votes applied to the remaining candidates. These steps are taken again and again, until someone has over 50% of the votes. Read more about how they work here