What is a Child Theme?
A ‘child theme’ is a WordPress theme with the same appearance and functionality as its ‘parent theme’. However, you can customize its files separately from its parent theme’s files.
More About Child Themes
Each time a new version of WordPress is released, a theme’s files must be updated to be compatible with the latest WordPress core. Therefore, if core theme files have been modified, that customization is lost with every WordPress update.
Child themes make it possible to keep these customized designs regardless of updates. WordPress users can only activate one child theme at a time.