Cotton candy is made by spinning heated and melted sugar into fine strands.
In a cotton-candy machine, granulated sugar is placed in a small central spinning head. Heat melts the sugar, and centrifugal force pushes the liquid through tiny holes around the head. As the sugar exits, it cools and solidifies into delicate threads that collect around the bowl. A paper stick or cone gathers the strands into the familiar fluffy cloud.
Cotton candy is mostly spun sugar, although commercial versions may include food coloring and flavoring. The airy appearance can make it look substantial, but the mass of sugar is relatively small compared with the volume because the strands contain many pockets of air. It is sometimes confused with caramel or corn syrup, but those are not the basic material named in this question. The treat is called candy floss in Britain and fairy floss in Australia, while “cotton candy” is the common term in the United States and Canada.