4K is just the latest generation of video tech, like Blu-ray and high definition but one generation newer. To exploit it you need a 4K TV and, for playing the discs, a 4K disc player.
Whether it’s worth it depends on how much you watch and what you watch. But it can be truly spectacular, which LOTR is. 2001 is also a great 4K disc.
I’ve had a 4k TV for about a year now and really, I don’t think it’s anything to write home about.
I see.... I have no TV so we’ll be okay in our primitiveness. :-)