This software is very clever, thanks to it everything will be perfect even if your TV can not be set at the same frequency of the video. Indeed it will change the framerate of the video to match the frequency of the TV.
This section is optional and only if you are not in bitstream and you need to adapt the framerate of the video to the frequency of your TV.
Almost all movies are shot at 24 frames per second but all DVDs sold in europe and PAL country are in 25 frames per second. From 24 to 25fps the studios speedup slightly the video and audio by 4.17%. This results in a film slightly shorter (2 hours film is 5 minutes shorter), which goes a little faster than the original and the soundtrack is more acute. All voices, music etc.. are more acute. This process is called PALSpeedUp. I suggest you to download these files to hear this effect :Buffy - Once More With Feeling - The Simpsons - Opening titles and credits. These examples are taken from this page.
On Blu-ray there is also a problem but it is different. Some Blu-ray are again in 25fps in PAL country but most are in 23.976fps. 23.976fps it's slightly slower than the original film (24fps) but it's imperceptible. The problem is that if your TV does not provide 24hz you will have to put it on 50hz or 60hz and then your TV will duplicate some of the images to be synchronized with the audio. It make movie stutter. And if you say, it's ok my TV support 24hz but no, the problem is certainly less visible but still there. Actually 23.976fps is not exactly 24hz so once again the movie stutters but this time much less. If your TV support 23.976hz indeed there is no problem for you. Often the TV show only 24hz but handle correctly 23.976 and 24hz its depends on your TV.
So if you want to cancel PalSpeedUp you have to put your TV on 24hz if it's compatible.
If your TV don't support 23.976hz for 23.976fps content, the best thing to do is to put your TV on 24hz and sync the video and audio on that frequency.
If your TV is not compatible with 24hz put it on 50hz and Reclock will take care to speed up or slow down the video and audio.
Double click on the installer of Reclock and let everything by default. You can access the setting by doing "Start menu / Reclock / Configure ReClock".