For the purpose of an informative piece (be it an article or essay), you will have a very distinct goal of teaching your audience or readers, by manner of presenting information (demonstrating), how to do something or give them enough information by manner of defining or describing something to where they could do something on their own.
Readers should visualize Steve trying to start his car while a crowd of people watch him. He is not able to start it and is not sure why. He knows that it is not out of gas, because he just filled it. A woman asks him what it means.
