GreatTeacher, the Canadian political system is different than the American. Canada models its parliament on the British House of Lords.
Now, pardon me if my ignorance is showing, but is a "riding" a voting district? Is it determined by population?
Yes. A riding is a voting district. Generally determined by population. Canada has 338 ridings.
http://www.ctvnews.ca/politics/election/election-2015-riding-map-of-canada
Also, are you just voting for prime minister or also representatives for parliament? The US splits those elections up, but I shouldn't assume it's the same everywhere.
We vote only for the representative in our riding. The leader of whichever party wins the most ridings becomes the Prime Minister.
And, is it "winner takes all" or is there proportional representation?
Winner takes all. Because we have a predominantly three party system here, we sometimes end up with a minority government. Which works out if the third party sides with the one who holds the most power. It doesn't work if the third party decides it doesn't like the party in power. Then...it is sometimes results in Canada going back to the polls in short order.