During driver's education courses, you learn what each road sign signifies. The two arrows converging means you need to merge. A squiggly arrow means the road winds. "Left Lane Ends" means, well, the left lane ends.
Sometimes you don't even need the signs to know what to expect. If you see a flurry of red brake lights, you know traffic is not moving. In an ice storm, if the car in front of you is skidding from side to side, you can bet that the road is slippery.