If it's not heavy it's likely got more poly in it than cotton, which depending on what you want to use it in can be good and bad. If you're going to do a lot of piecing with it, it will fray more, but stitch in the ditch keeps it pretty secure. I use it a lot for toddler and pre teen quilts. They need to be washed more, ya know?
Good to get free anything anymore...so have fun with it.