4K also called Ultra HD by some people. 4K refers to the resolution of the TV screen and the resolution of 4K is 3840*2160pixels. Now 2K TV is still selling, and it’s resolution is 1920*1080. Therefore, 4K is 4 times as many 2K. This likes camera, the higher of resolution, the clearer images you will get.
4K makes images looks vivid and clarity. You will won’t feel you are watching TV but looking things through a window.