What is Resolution of Monitor? Full HD vs 2K vs 4K

As you may know, many displays or monitors nowadays boast about having 4K UHD (Ultra HD); however, what exactly is 4K UHD, and how is it different from the Full HD we were used to seeing in the past?

1080p vs. 2K: What's the Difference and Is One Better? - History-Computer

4K Signal on 2K HD Displays

1440p vs. 4K: Which is the better choice?

2K resolution - Wikipedia

1080P vs 2K vs 4K Resolution - THINKWARE

Ultra HD vs. 4K TVs: What's the Difference?

Don't Buy the Wrong Resolution - 1080p vs 1440p vs 4K

PSA: 4k textures does not mean made for a 4k monitor, and 1080p users will benefit just as much : r/pcmasterrace

4K Vs 2K Resolutions On Monitors Compared

2K Resolution: Definition and Differences Between 4K, 2K and 1080p