If you have a WordPress blog and you would like to change your design a little bit or make some additional changes to your theme, it's not recommended to edit any of the theme files which you have installed. Instead it's always better to create a child theme and make all your editing into the actual child theme. It's very easy process to do if you know a little bit about HTML and if you follow simple steps from below.
So why it’s not recommended to edit original theme? Well most of the themes are getting updated and upgraded, so if in future you upgrade your theme to newer version, you will lost all editing you made before, but when you have additional changes in child theme, they will always remain there.To get better picture how easy it is, just watch this short tutorial video: