Montage theory

A montage is a collection of very short scenes, sometimes only a single shot each, designed to show a series of actions over time. Depending on the needs of the sequence, there are a few different options for how to write a montage in screenplay form.
Luv Kuleshov was among the very first to theorize about the relatively young medium of the cinema in the 1920's. He argued that editing a film is like constructing a building. Brick by brick  the building is raised. Or in this case 'shot by shot the film is made'
Luv Kuleshov a Russian director conducted an experiment that proves his point. He took an old film clip of a head shot of a noted Russian actor and inter-cut the shot with different images.

Example 
An hour or so into Sylvester Stallone's Rocky Balboa, he decides it's his destiny to strap on the gloves one more time. Bill Conti's theme music kicks in, and Rocky hits the floor for a set of one-armed push-ups, then lifts some heavy-looking metal chains and beats a side of beef. It's an inspirational, back-to-basics training montage.