BC-STV stand for a "single transferable vote". STV is a popular voting system currently used in Ireland and a number of Australian states in which voters rank candidates instead of only choosing one candidate. It provides more choice to the voter by allowing them to choose from a greater number of candidates, while achieving fair results.
The B.C. Citizens' Assembly on Electoral Reform recommended that British Columbia adopt a single transferable vote after looking at how people in a number of other countries votes and listening to concerns from people across B.C. who wanted fairer result, more accountable MLAs (Members of the Legislative Assembly), and a better way to choose between candidates on election day.
BC-STV has three major differences:
Giving voters more than one MLA to turn to.
Since two neighbours do not necessarily support the same candidate or party, there has to be more than one MLA representing the same geographical area if most voters are to have an MLA they support - that's why STV uses multi-member districts of between 2 and 7 members (more in more densely populated areas). Under BC-STV, you could end up electing a lawyer, a business owner, an environmentalist and a union organizer in one district. Almost every voter would have a candidate who matched their values and would be willing to champion their concerns.
Counting your next favourite candidate.
Counting is done in rounds and the candidate with the least voters after each round is removed. If a voter selects an independent candidate or a less popular candidate who is eliminated, their vote will count towards their second choice. Generally, voters will be able to rank two or more candidates from the same party, though they are also free to rank candidates from more than one party if they wish.
Treating all voters equally.
The Single Transferable Vote holds politicians accountable while delivering fair results.

Compare with BC's results.
