We just learned about the Display Resolution.
Another part of a computer monitor is the Display Refresh Rate.
When the computer screen is playing a video, or opening up a web page or showing something on the screen, it has to re-draw the screen for that picture very fast so that your eyes don't notice that it is changing, and so that it just looks like a real picture.
In old computers, the screen was drawn fresh every time starting from the top left, and going row by row from the top to the bottom.
Newer computers with LCD and LED monitors have smarter ways to redraw just some parts of the screen, but they still can only "refresh" the image on the page at a certain speed.
The speed that the screen can change and show a new image is called the Refresh Rate.
Our human eyes can only really tell if something is flickering if it is changing less than about 60 times per second.
If you think of that like a paper flip book showing an animation, you can usually see the flicker for those.
But if they were flipping so fast you couldn't tell, it would just look like an animated cartoon.
60 times per second is called the frequency, and is also the same as saying 60 Hertz or 60 Hz because Hertz means "per second".
Most monitors these days have a refresh rate of at least 60 Hz.
(from: wikipedia - refresh rate)
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