The 55PUS9109 has a maximum display resolution of 4K Ultra HD. That's over four times the display resolution of the most common HD type of Full HD. 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 amongst all TVs of a similar spec and age to the 55PUS9109.
A Full HD HD type is the worst display resolution amongst similar 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 televisions currently available including because of it's better review score, the Samsung UE65HU8200 (£2,079.00).