The highest display resolution of the UE48JU6400 is 4K Ultra HD. That's over four times the display resolution of a Full HD TV, which is the most frequently found display resolution. 4K Ultra HD TVs have a resolution of 3840 x 2160 pixels.
A 4K Ultra HD HD type is in fact the best display resolution across all comparable spec televisions that are a similar age to the UE48JU6400.
The worst display resolution amongst similar types of television is HD Ready.
4K Ultra HD TVs have a resolution of 3840 x 2160 pixels.
Alternative 4K Ultra HD TVs currently available that you might want to look at include the Panasonic TX-49CXX759, or the LG 40UF671 which has a better Rating; or the Samsung UE48JU6445 which is cheaper.