Fabric for Back to School Backpack tutorial

Hi there!  I'm new to sewing and found this website recently, where I now seem to be spending most of my time.   
I love the Back to School Backpack tutorial (http://sewmamasew.com/blog2/?p=9475) and would love to make one for my nephew who starts school this year. 
I've figured out all that I need except for one thing.  One of the fabrics needed is listed as "1 Fat Quarter White Fabric" which seems to be the white fabric with the designs in the photo.  I googled it and found the fatquartershop.com, but that's as far as I got. 
Am I on the right track?  Is it a different fabric than the rest of the backpack?  Any ideas?  Thanks so much!!!

A Fat Quarter is a unit of fabric measure.  It is a 1/4 yard of fabric but instead of being 9 inches wide by 44 inches (typical width of quilting fabric), it is 18 inches wide by 22 inches.

Hope that helps,
Kim

Perfect!  That makes sense.  I'm enjoying sewing, but it's like learning a completely new language.

Thanks for your help!