Software
What few people understand about software, is that software is like Swiss cheese. Full of holes, but only the ones that matter get found and fixed , by testing and through use. There will always be a few that matter and only show up later though.
Haven't you noticed how often your IPhone crashes ? At least they startup again so fast you are hardly aware. That is quality, whereas Windows stuff tends to just lock up until you shut it down & restart it yourself.
Software, an art of the unknown.
Whereas Testing sets out to find what its looking for, anything else being by accident.