Final answer:
An amicus curiae brief is a written brief submitted to the Court on behalf of a third party, and it means 'friend of the court'. These briefs are filed by interest groups or organizations that are not directly involved in the case but have a substantial interest in the outcome.
Step-by-step explanation:
A written brief submitted to the Court on behalf of a third party is referred to as an amicus curiae brief, which means friend of the court. These briefs are intended to influence the Court's decision by showing how such a decision may impact the general public or a specific population. Amicus curiae briefs are often filed by interest groups or organizations that are not directly involved in the case but have a substantial interest in the outcome.