If it wasn't for the Pokemon and Golden Sun series, I'd be a PlayStation fanboy. =/
No idea what this is, so I assume it's (in General Treister's voice) alien technology.
It's the next HD for HD, with up to 4 times the video quality of the current HD signal. There won't be much of a noticeable difference on anything smaller than 32" (and maybe not even on a 32"), but as the televisions grow in size, the quality of the image will become sharper. Whereas now, if you've ever seen a 70" TV, for example, you know that HD still isn't nearly as sharp as it is on a smaller TV, 4K technology will allow TV screens of up to (and I believe over) 100" in size, and still receive the same quality of video.
I've only read a little bit on it, but it's basically the next wave of features for a TV. We had HD 5-10 years ago, then it was 3D and now 4K is positioned to be the next selling feature of televisions.