WordPress child themes are the more stable option to customize your WordPress website.
A child theme inherits the functionality and styling of the parent theme. Child themes are generally developed to customize the parent theme.
It is the recommended way to customize the website theme without restricting the opportunity to update the parent theme.
For instance, if you edit the codes of the parent theme directly, you will not able to update the theme because when you update it, all the changes you made there will be lost. Hence, changes should be made via the child theme.
For example, if you are using a theme named OceanWP and need to edit the theme codes, instead of doing it directly on the theme code, make a child theme of it and do it on the child theme. If you edit the theme codes of OceanWP directly, you will lose your all changes after updating the theme.