It is a process in which a number of shorter shots are woven together in order to communicate a great deal of information in a short period of time. Montage is used to manipulate time, transcend vast spaces, and make connections between concurrent stories. A major purpose of montage is to create a narrative. A narrative is a chain of events,occuring in a given point in time, at a given point of space, where parts of it effect other parts. Major montage techniques used to produce narratives are linear, flashbacks, and cross or parallel editing which is used to track more than one story or character.
Montage is said to follow a grammar, a particular flow of shots.
Usually this involves a long or establishing shot to provide context. Then closer shots are inserted to provide more detail. For example, a scene within a house might start off with a shot of the entire house from a distance. Then show an inside shot which the audience has been conditioned to recognize as a scene occuring within the house shown in the previous shot. Another useful editing technique involves showing a reaction shot, usually a close-up or medium shot of a person.