Original: It is also clear from other writings and historical artifacts, however, that Socrates was not simply a character, or an invention, of Plato.
Simplified: While a lot of what Plato wrote about Socrates is accepted by historians, some people believe that Plato (who saw Socrates as a hero) portrayed Socrates as a much greater man than he actually was. Some people think that Plato was simply using the character of Socrates as a tool to express his own opinions rather than to accurately write about Socrates.