A Story Mode is a feature common in fighting games that focus on the plot of the game and/or the events of the playable characters, unlike most Arcade Modes which usually features a simple prologue and ending for a character (although this depends on the fighting game).
Street Fighter V is the first game in the series to feature a proper Story Mode (with the execption of the Street Fighter: The Movie home version game). There are two types; one is the "Character Story" mode and the other is a full fledged cinematic story mode titled A Shadow Falls which was released in June 2016 as a free DLC expansion.
This mode offers a background prologue of each playable character and the endings for each character sets up their role in A Shadow Falls.
Filling the gap between the events of Street Fighter IV and Street Fighter III, this cinematic story expansion depicts the ultimate battle between Shadaloo and the World Warriors who rise up against the evil organization. The mode can take three to four hours to finish and it comes in two difficulty levels, "Normal" and "Extra".