This means it's a synthetic material -- you see it wrapped around buildings that are under construction. It's strong, yet is cut easily with scissors. And you can stitch on it!
It's also used in US Postal envelopes. You can buy it, but I prefer the used envelopes. They always have really interesting patterns after their travels. And it's free! Although it's not terribly expensive to purchase.
I painted the inside of this envelope with Jacquard Lumiere paints, let it dry, then ironed it between two sheets of parchment paper. It does give off fumes, so I recommend doing it outdoors.
It gets a raised pebbly look on the side that the heat is applied. It's easy to heat it too much and then it gets holes.
I really like the way the sparkly bits in the paint get a kind of concentrated look after heating.