Relationship between CSS Editor and Child theme

Hello There,
I have selected the Intergalatic theme obtained on WordPress.com just recently (Fall 2014). I paid the small fee to “upgrade” and obtain the CSS option. I access the CSS by clicking “customize” and simply click on CSS. I have made several changes to the standard theme by adding lines in this CSS space.

Reading forums, I have noted many times it is advised to establish a child theme and i think the purpose is to make changes to that child theme versus potentially damaging the code for the original/parent code?

Question: when I use the CSS option in my simple little site, is this like using a child theme? or should i be doing a real child theme?

http://www.lightforyourway.com

thank you,