4k is a relatively new technology that has been around for just over 10 years. It is the latest in high definition televisions and movies which offer an incredible level of detail, vivid colors, and bright images.
The word “k” in the term is not a typo. There are several different ways to define what exactly constitutes as a resolution, but one of the more common ones is that it has 4000 pixels horizontally and 2000 pixels vertically. The number holds meaning because there were over 1000 lines on an old-fashioned TV screen which was scanned or refreshed at least 24 times per second for each frame.
With this definition, you can see how much clearer and smoother images become when using resolutions with these numbers. It’s also possible to get up close and personal with video games by playing them in full screen mode without any distortion from pixelation (noticeable fuzziness).
In general, TVs have been getting bigger over time while their screens have been getting thinner and more manageable. This is in part due to the popularity of higher resolution technologies such as HDTVs with resolutions of 1920x1080p, or 1080i that are progressively being replaced by true high definition (1920×1080) screens.
4K refers not only to TVs, but also to monitors with high resolutions. For example, hardware manufacturers now offer Hi-DPI displays which may also be called 4K monitors or retina displays.