Common knowledge (well known) or the act of making something widely known; often used for official notices or internal communications.
その情報は業界では周知の事実だ。
That information is a well-known fact in the industry.
会議の議題は全員に周知されている。
The meeting agenda has been made known to everyone.
安全対策を周知するためにメールで連絡した。
I sent an email to inform everyone about the safety measures.