Is muslin suppose to be see-through? I got some over the internet and it looks like cheesecloth it is so thin. I was planning on using it for my quilting but this fabric I have is unacceptable to me.

I had heard that some people use it for backing a quilt. Do they use this quality? Are there differing qualities to muslin?

Anyway, I had never used muslin before and was just wondering what you wise-ones had to say.
Thanks!