I use freezer paper for applique. You can either put it on you fabric with sticky side up and just press the seam allowance or shinny side to backside of fabric for achine applique.

It sounds like heat n'bond to me.
https://www.thermoweb.com/collections/heatnbond

When you fuse it to the fabric, does it leave anything behind? If not, then it's freezer paper. I love the stuff. I quit pinning tissue patterns to fabric. I traced the patterns onto freezer paper instead, and now just iron the pattern onto the fabric, which makes cutting the pieces out super easy.

Thank you everyone for your replies. I do not remember it being called freezer paper, which I did not think could be fused to fabric, but it sounds like that may be it. I have ordered some so we'll know soon.