Parent Child Themes

I didn’t know these existed, but apparently you can assign a child theme to a parent theme. A child theme inherits all the template files of the parent theme except for the style.css file and functions.php, which take precedence over the original. Ian Stewart of Themeshaper.com published a post ( Functions.php WordPress Child Themes ) which goes into detail on how to redesign your blog the smart way basing the work off of a theme framework. I’m still not sure about the usage of parent-child themes so any help you guys/gals could give me would be appreciated.