告示 (gào shi) is a public notice that is typically physically posted on a wall or board, like a sign. It is more concrete than 公告 (gōng gào), a formal public announcement from an authority, and different from 通知 (tōng zhī), which can be delivered verbally or digitally. It also contrasts with 启事 (qǐ shì), a classified ad for lost items or jobs.