When I read about these weather phenomena, I find that both of them depict the same thing, and have the same actions to avoid. So why are they differentiated?
A microburst is generally an intense down draft while wind shear can occur in any direction. It might be safe to say that a microburst is windshear but not all windshear is a microburst. From your linked pages
A microburst is intense small-scale downdraft produced by a thunderstorm or rain shower.
Windshear is any rapid change in wind direction and/or speed.