The Design Opportunity gives details about what you have been asked to create. Your writing can discuss criteria that must be met by the product. This can generally be done in one or two paragraphs.
The Design Brief gives specific details about what you plan to create. Although this is only one or two paragraphs long, the reader should quickly gain a vision of what your product will look like.
I have been asked to design and create a stool for the Seat It Project within Intro Design Tech class. My creation must fit within a box that is 250 x 250 x 350 mm, and it will be predominantly made out of birch plywood. Other available materials within the DT Lab include colored acrylic, paints, vinyl stickers, cushion, and fabric. I am required to include some aspect of digital fabrication into the product, such as an attachable piece of 3D printed plastic, a laser engraving, or a vinyl cut. This stool will be evaluated according to the design specifications that I will state before I begin creation. For base construction, I will be limited to choosing between a "crosslap design" and a "basic housing joint design." However, I will be free to choose the shape and appearance of the legs and top of my stool.
I will design and build a step stool as a gift for my wife, since she could use it to reach the upper parts of our house closets. The horizontal dimensions of the stool will be about 350 mm x 250 mm, and the height will be 250 mm. It will be useful as a seat or a step-stool. My stool base will make use of 4 housing joints cut into two thick wooden braces. The top will be a standard rectangle with rounded corners, but will be unique due to a laser cut acrylic inlay within 3 mm plywood. The wood will be stained a darker natural color and the acrylic will most likely be yellow and green.