Today, we'll take a quick look at the arcane art of ADR (aka looping). In short, ADR is the process of recording dialog after a scene has been shot, then editing it to match the rest of production sound as seamlessly as possible. This is done to replace otherwise unusable material.
ADR is defined here at filmsound.org and given fine treatment in this article on fromscripttodvd.com.
"...Without ADR, which is not really automated at all, unedited dialogue might sound like a distracting and unintelligible series of clipped and inaudible words. To gain a better appreciation of this task, you’re invited to meet Avram Gold, M.P.S.E, ADR and Dialogue Supervisor."
If I can get it to work, I'll post a short clip showing the step-by-step process. Enjoy.
(Extra nerd-points for anyone who knows how this entry's title is relevant to its subject.)