okay, this is image segmentation that attempts to estimate and remove the 'background' segments using some domain specific assumptions. This is generally referred to, in common language, as 'background subtraction'.
I will not debate common language use of 'background subtraction' because I have not discussed it with laypeople before, but what I can say is that if you were trying to implement what the article is trying to implement and were trying to find relevant literature, then searching for background subtraction would not turn up anything useful.
