Beyond adding functionality or content to a site, the other major task commonly performed by plugins is to augment, modify, or reduce information before it is displayed on the screen. This is done by using WordPress filter hooks, which allow plugins to register a custom function through the WordPress API to be called, since content is prepared before it is sent to the browser. In this recipe, you will learn how to implement your first filter callback function to modify the contents of the generator meta tag that is output as part of the site header.