How does the use of montage illustrate the intention of directors and what is its effect on the audience?

Definition:
Montage  is a technique in film editing in which a series of short shots are edited into a sequence to condense space, time, and information. The term has been used in various contexts. 
Usage: 
The author uses montage in Rockys montage to show months/years worth of training condensed down into 8 minutes to give the audience a sense of how hard Rocky is training and how much he improved from the begging.