There are many aspects to resolution, but for our needs, we’ll keep it simple. Resolution is simply a way to measure the size of the video being produced. Smaller images produce low resolution video, larger images produce HD or high definition video. It really is that simple. The larger the image being recorded, the higher the resolution and quality.
Resolution is measured in pixels. Then pixels are grouped into categories such as 2 megapixel, 4 megapixel, 5 megapixel and 8 megapixel. These categories are then simplified into 1K, 2K, 3K & 4K categories. This is intended to make things easier to understand but it often confuses the average shopper. The chart below will help clear things up.
Frame Rate or "Frames Per Second" FPS
The frame rate is how many individual images the camera produces every second. Hollywood movies for example are filmed at 24 frames per second. What we consider "live" video is 30 frames per second. Interestingly, the human eye has difficulty seeing the difference between 24 and 30 frames per second.
Why does this matter? The answer is cost. HD video produces huge amounts of data and large hard drives are required to store all that data. So why record in 30 frames per second if our eyes cannot tell the difference between 24 and 30 frames? By recording in 20fps you just dropped the hard drive size by 33% or increased your storage capability by 33%. Also, cameras that produce 20fps are generally lower cost than cameras that produce 30fps.
Have no doubt, the best video performance is produced with 4K cameras at 30 frames per second, but if you value cost over performance, consider 2K & 3K cameras with 15-20 frames per second. The video samples below provide a visual comparison.
30 Frames per Second - 4K
15 Frames per Second - 3K