Scenario is a narrative, which most commonly describes foreseeable interactions of user roles. A scenario has a goal, which is usually functional. Scenarios are frequently used as part of the system development process. Scenarios are written in plain language, with minimal technical details, so that stakeholders (designers, usability specialists, programmers, engineers, managers, marketing specialists, etc.) can have a common example which can focus their discussions. (Source: WikiPedia)
In the performing arts, a scenario (UK //, US //; from Italian: that which is pinned to the scenery; pronounced [*ʃeˈnaːrjo]) is a synoptical collage of an event or series of actions and events. In the Commedia dell'arte it was an outline of entrances, exits, and action describing the plot of a play, and was literally pinned to the back of the scenery. It is also known as canovaccio or "that which is pinned to the canvas" of which the scenery was constructed.
Surviving scenarios from the Renaissance contain little other than character names, brief descriptions of action, and references to specific lazzi with no further explanation. It is believed that a scenario formed the basis for a fully improvisational performance, though it is also likely that they were simple reminders of the plot for those members of the cast who were literate. Modern commedia troupes most often make use of a script with varying degrees of additional improvisation.
In the creation of an opera or ballet, a scenario is often developed initially to indicate how the original source, if any, is to be adapted and to summarize the aspects of character, staging, plot, etc. that can be expanded later in a fully developed libretto, or script. This sketch can be helpful in "pitching" the idea to a prospective producer, director or composer.