Where do you get household Pets from?

I know this is a pretty stupid question to ask but where do People get their Pets? Like household pets? E.g. Dogs, Cats. I never had a pet in Canada and Noone of the people I know have any pets or if they do I never get a proper response. I never owned any pets in my life. I am just trying to figure out where everyone gets their pets from. Do they Buy them? Do they just Find them in Shelters and Take them for Free? Does someone gift them? I never owned 1 and Am Thinking about getting 1 but I don’t know where to get them from. I Do Live in Vaughan so if someone can suggest where I can get them.