Not only does this trailer feature gameplay of Super Street Fighter IV for the Nintendo 3DS, it also details how Tag Mode for the game will work.
When players pass other Nintendo 3DS owners that have Street Fighter IV, they will automatically enter into short "figure-based" bouts, which are detailed in the video.
Another feature that the game has is that it allows players to challenge others who are currently in single player mode via WiFi in a style that is akin to the arcade version of Street Fighter IV.