These signs are essentially graphic rather than linguistic in nature. As such, their meaning tends to be easy to understand. Of course the meaning of some signs is less obvious than the meaning of others. On the International Roadsigns subpage I've placed images of the more important and confusing signs. Diamond signs indicate priority.
Red triangles are warnings.
Red circles are restrictions. Blue circles are requirements. Squares and rectangles give guidance. Note the signs which show two arrows pointing in opposite directions. If one of these arrows is red, it means the traffic traveling in that direction must yield to traffic traveling in the other direction.