The History and Techniques of Editing Explained in Less Than 7 Minutes
Why does editing work?
Why aren't moviegoers completely thrown for a loop when they see an edited film? I guess you could say it's because they don't really see it—the editing, anyway.
But this was a huge gamble made by filmmakers in the early days of cinema, who were blazing the trail of post-production and experimenting with continuity (a concept that didn't even exist back then), shot size, and angle.
One thing to take away from this, other than the bountiful facts about cinematic history, is the two major editing concepts: continuity editing and montage editing. Continuity editing is structural—it's meant to get you from point A to point B without wondering where you are. Soviet montage, on the other hand, works to elicit an emotional response from the audience.
These videos give great examples of each:
(Note: This video shows the different "methods" of montage developed by Eisenstein: metric, tonal, rhythmic, and intelligent.)