A written report: a document summarizing the results of an investigation, work, or other matters—widely used in schools, companies, and administrations.
上司にプロジェクトの報告書を提出した。
I submitted the project's report to my supervisor.
報告書は明日までにまとめてください。
Please finish the report by tomorrow.
会議では報告書の内容を簡潔に説明した。
At the meeting, I explained the contents of the report concisely.