Great collection of different types of cotton wicks for oil or ghee lamps kept for sale at the U. Market, Bangalore India.
These are primarily used for lighting a diya.
Following the encyclopaedia Britannica
thread, strip, or bundle of fibres that, by capillary action, draws up the oil of a lamp or the melted wax in a candle to be burned. By 1000 bc, wicks of vegetable fibres were used in saucer-type vessels containing olive oil or nut oil in order to provide light, and by 500–400 bc these wicks were in general domestic use.
wick in an oil lamp.