A child theme inherits the entire look and functionality of its parent theme. It lets you customize and extend the parent theme without modifying its files directly. This means your changes stay safe even when you update the parent theme.
Learn more about child themes here.
A child theme is already available for Reboot and can be downloaded here: Reboot Child.
Installing it is the same as the parent theme. To apply your customizations, make sure the child theme is activated.