4K is often considered as the same as UHD. However, there is something different between 4K and UHD. Simply put, 4K is more referring to 4096 x2160 video resolution or how the 4K contents are encoded, while UHD is more likely to mean 3840x2160 display resolution, for example, almost every TV and monitor you see advertised as 4K is actually UHD. Whatever, when referring to 4K UHD videos playback, they are the same thing.