Display resolutions explained
HD/720p and Full HD/1080p
High Definition or HD: The most basic was 1,280 pixels wide by 720 pixels tall, shortened to 720p. The lower-case "p" refers to “progressive scan”
'Full HD', a resolution which measures 1,920 x 1,080 pixels, often called 1080p
QHD/WQHD/1440p
QHD is four times the definition of standard 720p HD, meaning you can fit the same number of pixels as four HD displays into a QHD display of the same size, namely 2,560 x 1,440 pixels, or 1440p. QHD can also be referred to as WQHD (Wide Quad High Definition), it’s the same thing, but some manufacturers put a W in front of the QHD to show that it has a wide aspect ratio.
qHD
qHD is not to be confused with QHD. Despite having a very similar name, qHD stands for Quarter High Definition and is a display resolution of 960 x 540 pixels - one-quarter of 1080p Full HD.
4K and UHD/UHD-1
True 4K displays are used in professional production and digital cinemas and feature 4,096 x 2,160 pixels.
UHD is different because it is a consumer display and broadcast standard with a resolution four times that of a Full 1080p HD resolution: 3,840 x 2,160 pixels. The difference comes down to slightly different aspect ratios between digital cinema and home displays.
UHD is another 16:9 aspect ratio standard, which means screens are backward compatible with Full HD content.
5K and beyond
Not many manufacturers produce 5K panels. They can run at a resolution of 5,120 x 2,880. That's double the resolution of a QHD panel, which to the naked eye will still look razor sharp. 5K monitors are just in a league of their own. Of course with all those pixels, you'll need a multitude of graphics cards to consistently output over 60Hz.
read more and source: Expert Reviews