The context that changes the output.
WHAT TO INCLUDE IN THE BRIEF
Who the reader is, specifically What they already know What problem they have What you want them to do afterwards
The tone: formal, plain, conversational
The length What to include and what to avoid
AN EXAMPLE OF A POOR BRIEF
"Write an article about web hosting."
AN EXAMPLE OF A USEFUL ONE
"Write for a small business owner in Lagos who has never had a website and is unsure what hosting means. Plain language, no jargon, around six hundred words. Explain what hosting is, what they actually need, and what it costs roughly. End by telling them to ask us if unsure. Do not use technical terms without explaining them."
THE DIFFERENCE
The second produces something usable. The first produces filler.
WHAT PEOPLE OMIT MOST
The reader. Everything follows from who is reading.
REUSING BRIEFS
Once you have a brief that works for your audience, save it and reuse it.