24 fps films can’t fit on a 60 Hz screen, since 60 is not a multiple of 24. This problem can be overcome if the refresh rate is 120 or 240, both multiples of 24. But even though the TV can refresh its pixels at such a high rate, it can’t change the frame rate of the incoming data. Thus, TVs with higher refresh rates create extra frames
between those provided by the source. These frames are created by comparing and extrapolating information from successive source frames, and calculating the ‘in-between’ version. This reduces film judder, and creates a seamless transition between the existing frames.
However, many, including yours truly, deem this duplicated smoothness worse than the judder that results when the fps in the source and the refresh rate of the TV don’t match. The duplicated frames often make the output seem unreal, and can be a worse put-off than the judder! But of course, this is a matter of perception and taste, and is a personal choice.