Not that I'd ever buy an Apple, but I had some curiousity around what resolution a "Retina Display"

Not that I'd ever buy an Apple, but I had some curiousity around what resolution a "Retina Display" is in comparison with full HD since historically Apple's laptops have had fairly sucky resolutions.  Interesting to see their top of the line model go non-upgradeable & non-recyclable though.