What is 4K?
In general, there are two standards round 4k which are often mixed up, one is 4k and the other is UHD. Difference is the resolution of both, which is slightly different. This is related to the historical background.
Some Formats come from the consumer or professional field and other from the cinema usage. Resolution of UHD is 3840 x 2160 pixels which equals 4 Full HD Videos. 4K is 4096 x 2160 pixels which is targeted more for cinema usage as the image is wider and better adapted for cinema projections. What both standards offer is a much higher resolution, compared to Full HD Video and this is the actual benefit, a total new level of details.