A child theme is the name given to a WordPress theme which “inherits” its styles, templates and functions from a parent theme.
The parent theme and the child theme must both be present in the wp-content/themes directory, and the child theme is the one which must be activated.
If you have installed a theme from the WordPress themes repository, or purchased a premium theme from an online marketplace such as ThemeForest, it is always advisable to correctly configure a child theme in order that any future updates to the (now parent) theme will not copy over any customizations you make.
Most or our WooCommerce tutorials, for example, will assume you are able to place code snippets into the `functions.php` file in your theme. If you did this in a theme without using a child theme, you’d find, on update, you lost your snippets… and therefore the cool feature you’d make for your store!