op111.net explains how WordPress Child Themes work and what you need to make your own. The crucial line that separates ordinary themes from child themes it the Template declaration in the stylesheet: Template: Kubrick means you’re basing the child theme on the Kubrick theme.

The tutorial even touches Firebug usage and explains what several CSS rules do. Child themes shouldn’t be considered inferior or any different from normal themes: the goal to use good, existing code so you don’t have to reinvent the wheel, and can focus on implementing your custom idea instead. The question, now, is how you can pick a suitable parent theme.