what does it mean that a building is zoned R2, nonconforming legal triplex in Ontario Canada?

Question

Does it mean that the building is considered to be a residential house and not a commercial house, especially because it was built as triplex before the Ontario law, restricting residential buildings to two units, came out?

Answer 1

You are correct, that is what it means.

Answer 2

In the US, what that would mean is that it was legal as of the day it was built, so no enforcement can be taken against it as is, but it does NOT conform today, so there will be no permits given to alter it unless the planned alteration brings it into conformity, and it MIGHT mean that if it burns to the ground, it cannot be rebuilt as it is now. That's the important question to ask before buying such a place.