When I mentioned about a Scope's parallax, this means where the Scope's Len's are focused(generally) in Yards to give a person a clear, no double crosshair image(when moving head side to side or up and down). Also there will be an Eye Piece adjustable ring with lock-ring OR there will be what is called a "Fast Focus Eye Piece"(European Eye Piece) that adjusts to your sight to get the "Crosshairs" in focus. NOT TO BE ADJUSTED TO THE TARGET.
The fixed or adjustable power of a Scope has nothing to do with parallax.
Say a scope is Factory parallaxed at 50yds. This means that it's adjusted(lens) for actually between somewhere at 37 to maybe 65 yds. Rough estimate. Better the Scope, generally finer the parallax adjustments. When looking beyond probably 75 yds the target image will start getting a little hazy, and you'll start getting a "Crosshair Movement" when moving your Head. This is your parallax getting out of adjustment. Same when looking at Target at say 10yds also.
100yd parallax is adjusted for somewhere between 85 and 120yds. Looking through this type parallax, the Target Image might be very blurry if trying to shoot at Target at 30yds. It'll be like not wearing glasses and being "far sighted" and trying to see up close. Looking beyond 175/200yds the parallax won't be noticed as much, but it will be there. This is your normal hunting type scope that's used on millions of Centerfire type Rifles, and is usually a 3-9x40.
Again a 150yd parallaxed Scope is just like above, but parallaxed out further in yardage.
This is just a rough idea of how I learned it, and ONLY if you get a Scope "WITHOUT" an Adjustable Objective(A/O) you'll know what I mean when you start using it.
The A/O, or a Scope with a Side Focus knob, helps elliminate these parallaxes to fine tune a Scope and get the Target Image sharp and clear from as close as 5yds out to Enfinity. Lots of times though, even the A/O or SF yardage marks can be off. I like using a Lazer Range Finder to help find the true yardage to tell me how far my Scope's are off with their A/O or SF adjustments and it helps me to better range a distance in my Mind, when I don't have the Range Finder and out on a hunt, to keep my Scope and Rifle.within it's Kill Range I have them set at. After that, you start getting into Holdovers, Wind Adjustments and so forth.
My computer crashed last week and I lost lots of info I use/need, but the Internet has lots of good info about Scope Parallax and the terms used in how a Scope is made up in parts.
Hope this helps.