new to Quilting, please help

Hi to all of you! This may seem silly, but I have a question on materials to use for making a quilt. I grew up around my Grandmother and church ladies and their quilting, my mother taught me to sew my own clothes, and I sewed for my kids when they were little. However, I suppose this never really crossed my mind.. I usually bought poly/cotton blends, wools, etc to sew with, so am familiar with material. Now that I am not working, I would like to attempt to put a small quilt together. My scraps are mainly poly/cotton, but the quilt books call for 100% cotton. I perused the local fabric store until I was cross-eyed, looking at white 100% cotton, but there was also bolts labeled as 'muslin' that looked the same. I remember Grandma saying she used muslin for household items, like aprons, pillows, etc. Is there a difference and what do all of you use for white or neutral backgrounds or the backs of the quilts?
I love to read your entries on this forum, so many talented people here!
Thanks for any suggestions!

Kathy