A WordPress child theme takes the functionality of the main theme. It gives you the possibility to customize an existing theme. Instead of modifying the theme files directly, you can activate the child theme and work within it.
All customizations are stored in the child theme and anything in the child takes over the parent. So if the same file exist in both child and parent, the file from the child will control that aspect of the theme.
Working with child themes, your customizations are safeguarded from future upgrades because you only upgrade the parent theme, which you never edit, while the customizations are protected in your child theme which you don't upgrade.
Note : When you install one of our themes you must upload both parent and child theme folders to /wp-content/themes/ but you should only activate the Child theme via Appearance > Themes.