Dialogue replacement is mostly used when a video conveys high-impact information in longer segments and the content must sound native to the audience.
This voice to picture technique is more common in the entertainment industry as well as in certain types of employee training videos and product presentations, where the original language of each person on screen is replaced with the target language.
Dialogue replacement is more complex than UN-style voiceover because the international voice talent must match the tone, pace and emotions of the actor on screen.
It is, however, more cost effective, easier and less time consuming than a full lip-sync dubbing, as the goal is to match full phrases or time segments rather than the lip movements of the original actors.
The best results are reached when you hire one voice talent for each person on-camera.