I know they are called "silk flowers" and maybe the really expensive ones are made out of silk. They are true polyester, plastic, and wire hybrids. I don't think I would ever have them in my house. They are of the antithesis of everything I love about nature and using plant materials in design. But here I am, in the business of using them a lot. We resisted using fakes in the home staging business for as long as we could. But homes sit on the market. Fresh flowers die. The long lived orchid flowers eventually bite the dust and one can accumulate many, many orchid plants (no, really- you take this one!). So when we use fakes, we try and mix them with dried natural materials that we forage from the side of the road. Even though those are dead, they still have the echo of life.
These arrangments show the use of fakes, dried and a combination.