Bunting is a fabric
which is usually decorated with national colours, often made of cloth (cotton or worsted wool), polyester, nylon, plastic or even paper.
The best flags to use outdoors are made of nylon, as they are weatherproof, light and durable, and they wave easily in the breeze.
Cotton (bunting) flags look nice, but they aren't waterproof as they absorb a lot of water
. Nylon bunting doesn't hold water
. Nylon bunting repels it, making it a better choice.