WordPress themes come in different tiers that work together to create a user experience. A WordPress Child theme is a theme on the WordPress open-source platform that directly receives functional properties from a different WordPress theme, better labeled as a Parent theme.
WordPress Child themes are implemented in site design by developers who want to alter or fine-tune certain aspects of existing WordPress themes without sacrificing future upgrading functionality for the altered theme.
Formerly, there were no easy ways of applying updates to WordPress themes without jeopardizing customized styles and settings that were made outside of the themes core programming.
This issue was solved by implementing a tiered-theme system that many of us know as parent themes and child themes. The concept of a WordPress child theme is that it would gain total functionality, full features, and exact coding as a parent theme that allowed alterations and customizing styles to be input without the risk of losing the custom settings.
A WordPress child theme is a sub-theme to WordPress parent themes. Parent themes can also be a WordPress theme framework, but not all frameworks can be parent themes.