A chinois is a conical strainer with fine mesh. Liquids drain through while seeds, skin and other solids remain behind. A ladle or pestle may be used gently when the recipe calls for pressing a purée through it.
A coarse perforated cone strainer, often called a China cap, is not necessarily fine enough for the same finish. A chinois filters texture; it does not make an unsafe food safe.
Reference: Further reading.