The process prior to weaving, in which naturally unruly fibres are pulled though a comb to clean and straighten them, to align them neatly together, and to catch and remove very short lengths. After carding, all fibres are soft and ordered and ready to be spun.
Wool, even of the best quality, always needs to be carded. Other short fibres, such as cotton, wild silk, and all recycled materials that tend to be of lower quality can be made both useable and desirable through the carding process. Only long filament fibres–of the best cottons and silks for example–don’t require this process.