Narrative - Three Act Structure

Act 1: is the first act of the film, usually is the first section of the film.
Act 1 starts and sets up the film, there is a point which introduces the characters and lets the audience see what type of character they are and how they act.

The main character has a target to reach, this turns out to be the main focus of the film. An incident gets the plot of the film started halfway through the first act. 

Act 2: is the second act of the film, it takes up the last half of the film. 
In act 2 there are problems, which prevent the main character from achieving what they need to. 

The first Culmination is just before halfway through the film, the main character almost reaches their target. However a problem usually occurs  

At the midpoint the main character reaches their weakest and lowest point in the film as they seem too far away from reaching their target. 

Act 3: is the final act of the film, this is the final section of the film.
 
The climax is when the plot of the film reaches its biggest tension between the two opposite sides.