Worsted vs Woolen flannel

[IJReilly]

I recently read this article:

http://putthison.com/post/23674835650/worsted-vs-woolen-flannels-i-love-wool-flannel

I have previously been under the impression that flannel pants were delicate, but the above article explains that not all flannels are equally sensitive. However, it does not go into great detail regarding how to identify worsted flannel. Can somebody provide a more detailed explanation?

Thanks.