Oudh or Agarwood is a dark resinous heartwood that is formed in Aquilaria and Gyrinops trees when infected by a type of mould.As the infection progresses the tree produces a dark aromatic resin. The aroma is complex and pleasing with very few similar articles in nature.Dehn Al Oudh refers to the oil extracted from the wood via hydro-distillation. By weight it can be worth more than gold and has has been referred to as "liquid gold".Oudh or the agarwood from where it is extracted may be burned directly as incense and used to scent one's home.As with any natural product, Oudh will vary according to region, quality, rarity and the age of the wood/oil and many other factors. Hence a signifiant variation in prices.