Post-sync is based on adding and synchronizing a recorded sound or voice over an existing recorded visual material, for example adding an actor’s voice over an animation character (source Wikipedia).
Commonly this post-production element is also called dubbing, outside the film-industry, as a synonym of revoicing. This means replacing the original actor’s voices with better fitting ones or with voices performing in other languages. In many countries worldwide, post-sync is systematically used for most productions coming from foreign countries.
Oftentimes actors are also dubbers, and dubbers are also actors, but it is not always the case. Above all in those countries in which post-sync is widespread, there are many speakers/dubbers that make a living out of this activity. It is common knowledge that the Italian dubbing school is very renowned for it quality and expertise, as it has developed as one of the first ones in the early ’30s of last century.
Sometimes the success of movies or TV shows can be found into the mastery of the post-sync process. Often it happens that the performance of the Italian voice, for example, is exquisite or incisive conquering the audience much more than the original performance. Some other times it is the tone or the voice itself that makes the character unforgettable, whether it is an actor in the flesh or an animation character.
Post-sync can therefore be defined as the process of replacing recorded voices with either the original actor dubbing him/herself or another language native performer recording his/her voice to make the material available in other languages or, as said before, an actor recording the voice of an animated character.
The process of replacing the original voice by the original actor him/herself is also referred to as ADR, an acronym standing for Automated Dialog Replacement. Mostly it is used to better sync the transitions, correcting accents or pronunciations, or to highlight comedic or dramatic timing.