MGFX4 - Matthew Ashby

"What does this clip depict that is impossible?"
The idea that shared dreaming is accomplished with a machine and is honed as a skill set which can then be used for idea robbing or planting.
"What visual effects does it use?"
As an analogy for film creation, this clip of Inception uses jump cut editing, and 3d environmental rendering to create the illusion that the characters are in a dream and thus able to mentally control their surroundings.
"Why these effects?"
These effects create a sense of control even in the midst of the chaos, playing off the actress's performance to make it seem as if she is surprised that she is the cause of the explosions.