Child themes make customizing your theme easy. Many times, you want to edit the theme's php files but forgot what you edited and what needs to changed in the new theme. Child themes can help you solve this problem. A WordPress Child theme derive its functionality from the parent theme, and then override the styles and functionality you want to modify without directly changing the parent theme.
Creating a Child Theme:
Theme Name: parenttheme Child
Description: Child theme for the parenttheme theme
Author: Your name here