Wait
Its actually a thing?
How does that even work? Seriously i dont understand computers at all.
It depends on what your exact specs of your computer are, but consider this (I don't know what your build is that you showed your buddy, I'm just going to assume you chose a dual core CPU and a very powerful GPU):
Let's say you're playing a pretty demanding game, like the latest Total War games. These games, in battles, have a lot of CPU calculations going on as well as a plenty rendering needed from the GPU. If you're running on high graphics settings with like a ton of calculations going on with your powerful GPU, the game will have no problem making everything look pretty, but because your CPU is pretty weak relative to your GPU, the game is gonna stutter and look a bit of a slideshow because the processor only has so much power to do many, many calculations.
tl;dr: game look pretty but run slow because math cant be done quick enough