Many circumstances may entitle an immigrant to a temporary work permit in Canada, but many of those apply to immigrants that are already in Canada, usually people that are destitute and cannot be sent back to their country. It would be the case for people that cannot be deported yet, that ask for political asylum, or ask to stay in the country based on humanitarian grounds, or people that get special permits to remain in Canada.
Three, indeed two types of permits will be of interest for most people abroad. The third kind is more exceptional. It applies to people from the US or from countries that Canada has a special agreement with in terms of labour mobility.