What does a downward-pointing triangle sign mean?

A downward-pointing (inverted) triangle, usually red and white, is a YIELD sign. It means you must slow down, be prepared to stop, and give the right of way to traffic and pedestrians in or approaching the intersection or roadway you are entering. Unlike a stop sign, you need not always come to a complete stop, but you must yield and only proceed when it is safe. The triangle shape is reserved for yield signs. Recognizing the yield sign and understanding the difference between yielding (give way, stop if needed) and stopping (always full stop) is standard regulatory-sign content.