What you end up with is a smoother flowing picture, but it's dependant on the source, and the particular t.v.'s ability to deal with the input.
The most common refresh rate for today's Televisions are 60hz for NTSC-based systems and 50hz for PAL-based systems. However, with the introduction of some Blu-ray Disc and HD-DVD players that can actually output a 24 frame per second video signal, instead of the traditional 30 frame per second video signal, new refresh rates are being implemented by some television display makers to accommodate these signals in the correct mathematical ratio.
If you have a TV with a 120hz refresh rate that is 1080p/24 compatible (1920 pixels across the screen vs 1080 pixels down the screen, with a 24 frame per second rate). The TV ends up displaying 24 separate frames every second, but repeats each frame according to the refresh rate of the TV. In the case of 120hz each frame would be displayed 5 times within each 24th of a second.
In other words, even with higher refresh rates, there are still only 24 separate frames displayed every second, but they may need to be displayed multiple times, depending on the refresh rate.
To display 24 frames per second on a TV with a 120hz refresh rate, each frame is repeated 5 times every 24th of a second.
To display 24 frames per second on a TV with a 72hz refresh rate, each frame is repeated 3 times every 24th of a second.
To display 30 frames per second on a TV with a 60 hz refresh rate, each frame is repeated 2 times every 30th of a second.
To display 25 frames per second on a TV with a 50 hz refresh rate (PAL Countries), each frame is repeated 2 times every 25th of a second.
To display 25 frames per second on a TV with a 100 hz refresh rate (PAL Countries), each frame is repeated 4 times every 25th of a second.
If the television is also required to do a 24 frame per second to 30 frame per second or vice versa frame rate conversion, then you also have to deal with 3:2 or 2:3 Pulldown as well where the 24 frames of film will be stretched onto 30 frames.
