High dynamic range imaging (HDR) is a technique used in imaging and photography to reproduce a greater dynamic range of luminosity than is possible with standard digital imaging or photographic techniques. The aim is to present the human eye with a similar range of luminance to that which, through the visual system, is familiar in everyday life. The human eye, through adaptation of the iris and other methods, adjusts constantly to the broad dynamic changes ubiquitous in our environment. The brain continuously interprets this information so that a viewer can see in a wide range of light conditions.
For imaging, HDR, as its name implies, is a method that aims to add more “dynamic range” to photographs, where dynamic range is the ratio of light to dark in a photograph. In principle, when HDR is enabled during that image capture, the camera instead of taking one photo, three photos are taken at different light exposures. Then, either with an automatic software (as is done at Mobile Phone cameras) or with a sophisticated image editing software, the pictures with the different exposures are overlayed and the best parts of each photo are highlighted.
Toward the HDR TVs, the UHD Alliance (UHDA)  of TV manufacturers, broadcasters and film producers have decided to create a new brand logo beyond UHD, the Ultra HD Premium that defines the technical specifications that a TV must meet in order to deliver a HDR/premium 4K experience.
The UHDA’s new ULTRA HD PREMIUM specifications cover multiple display technologies and reference established industry standards and recommended practices from the Consumer Technology Association, the Society of Motion Picture and Television Engineers, the International Telecommunications Union and others. Moving further forward, UHDA Launches “ULTRA HD PREMIUM” Logo and Certification Licensing for Ultra HD Blu-ray Disc Players.
Summarizing the minimum requirements :
Minimum resolution of 3,840 x 2,160 – which remains the same as the 4K/Ultra HD TVs.
10-bit color depth – In contrast to the 8-bit color space that Blu-Ray players use today, the UHD Premium TVs must be able to receive and process a 10-bit colour signal, often called ‘deep color’, supporting over a billion colors.
Minimum of 90% of P3 colors – To certify a TV as an Ultra HD Premium TV, the TV must be able to display 90% of the colors defined by the P3 color space  (More info here).
Signal Input– BT.2020 color representation 
High Dynamic Range – SMPTE ST2084 EOTF 
Minimum dynamic range – To qualify with UHD Premium, a TV should meet a minimum standard for the maximum and the minimum brightness it can achieve.
- Aiming at LED TVs: More than 1,000 nits peak brightness and less than 0.05nits black level
- Aiming at OLED TVs: More than 540 nits brightness and less than 0.0005 nits black level
Please note that TVs could be certified Ultra HD Premium retroactively, but few TVs released in 2015 can meet the standard.