Gobo
An opaque cut-out or template placed in a light's beam to cast a shaped pattern onto a subject or background.
In depth
The word contracts 'goes between' — anything between light and subject that shapes the beam counts, from a purpose-cut steel template in a projection attachment to a piece of card with slots taped over a speedlight. Patterned gobos add narrative texture: window frames, blinds, foliage, all suggesting a place the studio does not have.
Examples in practice
A window-frame gobo projected onto a plain wall makes a studio portrait read as if shot in a sunlit room.