Storyboard
A shot-by-shot visual plan of the piece, in sequence.
A storyboard draws the film before it exists: one frame per shot, in order, with what happens in each. It can be sketches, reference stills, or rough frames. The fidelity matters far less than the sequence.
It answers a question no other document does: does this actually cut together? Ideas that read beautifully in a brief sometimes turn out to have no visual variety, or to require three impossible transitions in a row. A storyboard makes that visible while it's still free to fix.
It earns its cost on pieces with a defined narrative and a fixed running time: ads, brand films, anything scripted. On documentary or interview-led work it's usually the wrong tool, and a moodboard plus a shot list gets you further.