A WordPress child theme is a secondary theme that “sits atop” a parent theme or primary theme.
In order to use a child theme, you must have the parent theme installed. The child theme, will be the active theme, however.
The advantages of using a child theme include:
- Protect your blog setting and customizations when updates are made to the parent theme.
- You can safely add custom CSS or other code changes to your blog without worry.
If you add custom code directly to a parent theme, it will get erased with the next theme update. This makes child themes a safe choice for those who like to DIY their site or need to add custom code or scripts.