Meng

Retina is Apple's marketing term for displays with a high enough ppi that at the normal viewing distance you can't distinguish any of the individual pixels no matter how hard you try. You could technically label basically every android flagship and most 4K displays and TVs "Retina" as well. 
 
That's just because Apple uses really nice screens. You can get really nice standalone monitors for your PC with a similar res and colors. 
 
^^ 1440p is a much better option for gaming. 4K is great for screen real estate and text, but in games there's barely any noticeable difference on the same size panel. LTT actually made a nice video on that subject: 
 

I don't know what panels they use, and Apple uses glossy screens vs the matte/satin ones most PC laptops have. I forget who the laptop pros on this forum are, they might know. 

Thank you! That is very helpful!

lol thanks! this "Because Apple and gaming do not really go together " will probably be self-explanatory.