Gum arabic is a substance is taken from two sub-Saharan species of the acacia tree. It is used primarily in the food industry as a stabilizer, but has had more varied uses in the past, including viscosity control in inks.
The gum is produced by the trees in question as a way of resealing the plant's bark in the event of damage -- a process called gummosis.
Gum arabic is a complex mixture of saccharides and glycoproteins, which gives it one of its most useful properties: it is perfectly edible. Other substances have replaced it in situations where toxicity is not an issue, as the proportions of the various chemicals in gum arabic varies widely and make its reliable performance troublesome. Still, it remains an important ingredient in soft drink syrups, "hard" gummy candies like gumdrops, and in marshmallows. Pharmaceuticals and cosmetics also use the gum.
The substance is grown commercially throughout the Sahel from Senegal to Sudan. Oddly, the connection between the latter country and Osama bin Laden brought the otherwise undistinguished gum to public consciousness in 2001, as an urban legend arose that bin Laden owned a significant fraction of the gum arabic production in the Sudan, and that therefore one should boycott products using it.
This story took on somewhat significant proportions, mostly thanks to an article in The Daily Telegraph a few days after the September 11, 2001 Terrorist Attacks, which echoed this claim. Eventually the US State Department issued a release stating that while Osama bin Laden had once had considerable holdings in Sudanese gum arabic production, he divested himself of these when he was expelled from Sudan in 1996.