What is Single Transferable Voting? 

Clear, clean, short - best introductory description I've found! It's so good that you can easily imagine how it would work in multiple candidate elections. But I wish vid-maker would also do a separate vid on multiple-candidate elections.

The system you're using is actually called Instant Runoff Vote. Single Transferable Vote is used to determine multiple winners in multi-member districts and includes voting thresholds so that if the first winners hog too many votes, some of those votes are redistributed until all seats in the district are filled. Otherwise, it is similar.