A mood board is a type of visual presentation or 'collage' consisting of images, text, and samples of objects in a composition.
Amateur and professional designers alike may use them as an aid for more subjective purposes such as how they want to decorate their bedroom, or the vibe they want to convey through their fashion.
[1] Mood boards can also be used by authors to visually explain a certain style of writing, or an imaginary setting for a story line.
In short, mood boards are not limited to interior decorating purposes, but serve as a visual tool to quickly inform others of the overall "feel" (or "flow") of an idea.
They are used to help creative teams stay on the same page while also adhering to the image that the brand wants to project outward.