Advanced Customization – Theme’s Child Usage
To let you – premium theme users – customize WP themes developed by TheThe Fly even more, we suggest that you use the Parent-Child theme mechanism offered by WordPress (source: http://codex.wordpress.org/Child_Themes).
The main benefit of using the Child theme instead of your default Parent one to customize your WordPress blog is the fact that you do not loose your customization on the theme’s update. Only Parent theme’s files are usually overwritten during a theme update.