The UE40KU6400 has a maximum display resolution of 4K Ultra HD. That's over four times the display resolution of a Full HD television, which is the most frequently found display resolution. 4K Ultra HD TVs have a resolution of 3840 x 2160 pixels.
This TV's display resolution (4K Ultra HD) is in fact the best display resolution across all new similar spec TVs.
An HD Ready HD type is the worst display resolution across comparable types of TV.
4K Ultra HD TVs have a resolution of 3840 x 2160 pixels.
It may also be worth also looking at one of the alternative 4K Ultra HD TVs currently available including because of it's better review score, the Samsung UE40KU6000, the Philips 43PUS6101, or the LG 49UH620.