Viscose is synonymous with rayon, and the name comes from the honey-like texture that occurs during the manufacturing process. The main ingredient in viscose is wood pulp, making it hard to classify as either synthetic or natural. Though the wood pulp makes it natural, the manufacturing process (a very polluting one) is very much driven by man.
Rayon fabric is wrinkle-resistant. This means if the fabric is scrunched up in a fist, it can retain its original shape back. However, cotton can wrinkle easily and will require good ironing to smoothen back to its original shape.