I'm looking at [Webmonkey's PHP and MySql Tutorial, Lesson 2](http://www.webmonkey.com/2010/02/php_and_mysql_tutorial_-_lesson_2). I think it's a php literal. What does `%s` mean? It's inside the `print_f()` function in the while loops in at least the first couple of code blocks.

`printf("<tr><td>%s %s</td><td>%s</td></tr>n", ...`