What it means
A brief is the set of instructions and materials a solicitor delivers to a barrister to advise on or appear in a matter. It typically includes the relevant documents, pleadings, evidence and a memorandum of instructions. To "brief counsel" means to engage a barrister on a case. The contents of a brief are usually confidential and may be protected by legal professional privilege.
How it's used
The solicitor sent the barrister a brief containing the contract, the pleadings and the witness statements.