When I used to be smart and was studying astrophysics, I understood how parallax calculations were used to judge vast distances in space. As a photographer, I spend most of my time dealing with some level of lens distortion while taking pictures. Fast forward to utilizing firearms and you find that parallax comes into play when speaking about any level of optic. I use red dot sights on my carbines. I use a red dot sight on my pistol. I never gave the science behind it a lot of thought beyond “put that dot on a target and pull the trigger.”
Dave Merrill just published a fantastic article on the marketing term of “Parallax Free” when it comes to red dots, and why you should always have a healthy dose of skepticism while researching which optic may be best for you.
Absolutely spend the few minutes reading this article and watching the video so that you can weed through any misinformation out there.