A message is a piece of information that contains a combination of ideas, facts, opinions, feelings or attitudes. A message is something that is considered important for the audience to know or do. You may have only one message that you want to convey and you may want to modify this message for several different audiences. It is more than likely that you will have three or four key messages, and will want to tailor them for three or four audiences using different tools.
The content of the message could be organised in different ways so that it is more likely to persuade or convince people. These are called appeals. Not everyone responds in the same way. What might persuade you to do something might be quite different from what might persuade another person. The type of appeals that could convince people with little or no schooling might be different from those that convince people with a higher educational level. Children might respond to the message differently from older people and so forth.
A major error made in many health education communications is the tendency to use arguments that rely heavily on too many medical details which can confuse the audience.