This is from an Article in WIKIPEDIA titled: Moving image formats
Is it just me, or does it make no sense?
"Moving image formats"
Image change rate
There are several agreed standard image change rates (or frame rates) in use today: 24 Hz, 25 Hz, 30 Hz, 50 Hz, and 60 Hz. Technical details related to the backwards-compatible addition of color to the NTSC signal caused other variants to appear: 24/1.001 Hz, 30/1.001 Hz, 60/1.001 Hz.
The image change rate fundamentally affects how "fluid" the motion it captures will look on the screen. Moving image material, based on this, is sometimes roughly divided into 2 groups: the so called film-based material, where the image of the scene is captured by camera 24 times a second (24 Hz), and the video-based material, where the image is captured 50 or ~60 times a second.
The 50 and ~60 Hz material captures motion very well, and it looks very fluid on the screen. The 24 Hz material, in principle, captures motion satisfactorily, however because it is usually displayed at least at twice the capture rate in cinema and on CRT TV (to avoid flicker), it is not considered to be capable of transmitting "fluid" motion. It is nevertheless continued to be used for filming movies due to the unique artistic impression arising exactly from the slow image change rate.
25 Hz material for all practical purposes looks and feels the same as 24 Hz material. 30 Hz material is in the middle between 24 and 50 Hz material in terms of "fluidity" of the motion it captures, however it is also handled in TV systems similarly to 24 Hz material (i.e. displayed at at least twice the capture rate).