What does this road sign mean?

An octagonal sign always means stop. When approaching a stop sign, you must come to a complete stop at the marked stop line and proceed only when it is safe to do so. If there is no stop line, stop before the crosswalk. If there is no crosswalk, stop before the intersection at a point from which you can see any oncoming traffic.

• Slow down and prepare to stop if cars are approaching you.
• Come to a full stop then proceed when it is safe to do so.
• Proceed carefully through the intersection, not always stopping.