Zim 240Hz (240 times each pixel of the monitor is refreshed in one second) and taking into account these 60 fps (The graphics card throws out 60 individual images, also in one second). Simplifying it, it turns out that the monitor will refresh its pixels four times for one image generated by the graphics card. All this tends to the fact that the monitor with 240Hz will be "limited" by the FPS setting on the graphics card, which is 60 here. An expensive matter for how we perceive the image is the issue of synchronizing the frames per second of the graphics card with the Hz on your screen. You've probably heard of VSync, GSync, FreeSync. Technologies that try to synchronize these two frequencies. The problem is that when we turn on VSync, the frames generated by the graphics "wait" at times to be displayed on the screen, so they are not always displayed as quickly as we would like. The second, potentially more serious drawback is the problem of "choking" the image - VSync helps in situations where the number of frames produced by the graphics card is too large compared to what the monitor wants to display. In the opposite scenario, where the graphics are not able to generate the 240 frames expected by the display, because more is happening on the screen than the GPU is able to process. Frame drops become much more noticeable with VSync enabled. This causes image stutter, which can be much more annoying than tearing.
Nvidia decided to approach the synchronization problem from the ass - instead of forcing the graphics card to synchronize with the frequency of the monitor. G-sync technology makes the monitor try to match its refresh rate to the number of frames produced by the graphics.
As a result, frame drops are much less noticeable, as the monitor transitions quite smoothly between their different values. Delays in response to keystrokes are imperceptible.
FreeSync is AMD's answer to Nvidia's GSync solutions. Basically it's the same.
What is the optimal frequency in first person shooter games so that we can react relatively quickly or even see some movement? World research shows that it is only from 7 to 13 Hz, i.e. 7 to 13 images in one second. This means that while playing, watching TV or even in real life, the remaining frames are just an interpretation of our brain.
It is also interesting that professional film studios use a 24-frame standard. An exception is, for example, the trilogy of films about Hobbits by Peter Jackson. He decided to record it at 48 fps.