4K is a video specification that literally just means ‘4,000’. It gets its name from the approximately 4,000 pixels of width of the footage.
4K resolution, also called 4K, refers to a horizontal resolution on the order of 4,000 pixels and vertical resolution on the order of 2,000 pixels. Several 4K resolutions exist in the fields of digital television and digital cinematography. In the movie projection industry.
4K format was named because it has 4000 pixels horizontal resolution approximately. Meanwhile, standard 1080p and 720p resolutions were named because of its vertical resolution. The new standard renders more than four times higher image definition than 1080p resolutions for example.
Display resolution: minimum of 3840 x 2160 pixels
4K display has to consist of at least 3,840 pixels (horizontal) x 2,160 pixels (vertical) of resolution and the horizontal can go above 4,000 pixels. This puts it on the top of the current scale of digital resolutions in which the bottom is occupied by standard definition TV (450X540 pixels), HD with 720 pixels and full HD at 1080p.
In simplest terms, if you measure HD resolution by vertical pixel height (720p, 1080p) then 4K UHD can also be called 2160p.
The top three reasons that 4K video:
1. Resolving Detail
2. Closer Viewing
3. Scaling Down