I use for knits, it keeps the fabric stable when embroidering and the surplus is easily removed afterwards.

I also use this when embroidering on lightweight cotton. I tend to pull at my fabric after hooping (a no-no) and this kind of stabilizer helps.

I use it for my felt toilet paper covers. You will have fun experimenting.

You can use it on just about anything, knits, cotton, anything. You just want to weigh the cost of using it on anything. Usually the iron on is more expensive than, say, a regular tear-away. So I wouldn't want to use an iron on tear-a-way when a regular tear-a-way would work or a cut-a-way.