I am learning PHP and mySQL from Wrox's PHP Programming. I am stuck on a code and can't understand what does it means. Its basically a function and what it does is formats the text inside the function. Here is the code:

PHP Code:
function GenerateHTMLHeader($message
printf("font size=+4 face=Arial color="red"><B>");

When we type GenerateHTMLHeader("Omair Haroon");
it would display Omair Haroon in red color.

The only thing I can't understand is what does %s in the fourth line stands for.

Waiting for your help guys.