Ahh, you are asking a question on "What is Storyboarding?" you say?
Storyboarding is basically an animation featuring 2D images which can be moved, scaled, rotated or coloured.
A storyboard was initially made when INIS wanted to create storylines that played throughout the level with pass and fail animations. Throughout the ten years of the game, it has vastly improved thanks to Damnae, 11t (who passed away in 2018), Exile-, StarrodKirby86, ztrot. Even the tutorial that you played was all done with a single storyboard (the voices are sounds added into the storyboard).
Now we have storyboards that can even push the limits of what osu! can even do, like 3D animated boxes using only 4 images.