Originally Posted by Zeusecho
I think the term parallax adjustment is confusing or not correct.
It's really a focus knob and by setting the focus correctly you eliminate parallax error (seeing two images).
Is this correct?
For all practical purposes, yes.
If you're an expert rifleman, and good at doping wind, mirage, and measuring range with a laser, it can be a very good addition. For the average shooter, it's like a spoiler on a Chevy Volt. Looks "Kewl" but doesn't do much for you.
OTOH, it most certainly won't hurt anything, so if you want it, then get it!