1. Binder / Stabilizer – Retains the physical characteristics of food/cosmetics and ensure the mixture remains in an even state.
2. Bulking Agent – Non-nutritious or inactive substances added to increase stability of the mixture.
3. Emulsifier – Allows water and oils to remain mixed together to form an emulsion, such as in mayonnaise, ice cream, and homogenized milk
4. Fragrance / Fragrance Component – Provides or enhances a particular smell or odor.
5. Gelling Agent / Thickener – Increases the viscosity by thickening the liquid to give it more texture
Xanthan Gum is a natural carbohydrate produced by fermenting glucose with the appropriate micro organisms (Xanthomonas campestris). It is gluten-free but can be used as a substitute for gluten (the protein which gives wheat flour its structure).
In foods, xanthan gum (E number 415) is common in salad dressings and sauces. It helps to prevent oil separation by stabilizing the emulsion, although it is not an emulsifier. Xanthan gum also helps suspend solid particles, such as spices. Xanthan gum helps create the desired texture in many ice creams. Toothpaste often contains xanthan gum as a binder to keep the product uniform. Xanthan gum also helps thicken commercial egg substitutes made from egg whites, to replace the fat and emulsifiers found in yolks. It is also a preferred method of thickening liquids for those with swallowing disorders, since it does not change the color or flavor of foods or beverages at typical use levels. In gluten-free baking xanthan gum is used to give the dough or batter the stickiness that would otherwise be achieved with gluten. In most foods, it is used at concentrations of 0.5% or less. 
In cosmetics, xanthan gum is used to prepare water gels, usually in conjunction with bentonite clays. It is also used in oil-in-water emulsions to help stabilize the oil droplets against coalescence. It has some skin hydrating properties. Xanthan gum is a common ingredient in fake blood recipes, and in gunge/slime. 
Recent Findings :
Xanthan gum can be used to manage those with diabetes mellitus.  It is relatively safe even with consumption of up to 12g/day in muffins.  It lowered fasting levels and "reduced fasting levels of total plasma cholesterol in diabetic subjects". "Subjects also reported a sense of fullness after consuming xanthan muffins with no severe digestives symptoms".  Xanthan gum is also used to thicken the batter of gluten-free muffins which also improved their appearance and volume. 
Xanthan gum in a gel form also showed no significant effects from plasma biochemistry to glucose tolerance and triglyceride/phospholipid/HDL cholesterol levels.  In a study conducted on rats, the combination of xanthan gum and guar gum has an "improved hypolipidemic effect (lipid-lowering effect)" on non-diabetic and diabetic rats.  Xanthan gum is able to inhibit lipid and protein oxidation which leads to an increased rate of lipid digestion.  The ingestion of xanthan "caused no adverse dietary nor physiological effects in any of the subjects". 
Xanthan gum has a synergistic effect with other gums/gum-like substances such as guar gum , locust bean gum , galactomannans , glucomannan   , pectins  and cellulose  in other to control viscosity. A 1:1 mixture of xanthan gum and locust bean gum is also the most effective gum combination at inhibiting "glucose movement" in vitro.  The acidification of this gum combination by gastric juice turned the most viscous gum combination into the least viscous.  Reneutralization increased the viscosity again although only at one-third of its original value. It is hypothesized that the flexibility of viscosity of this gum combination at different pH contributes to its ability to slow gastric emptying more than the other gum combinations in order to control blood glucose levels.  A 1:1 mixture of xanthan gum and cellulose also has a similar effect in slowing gastric emptying while also increasing the volume of water in the small intestines.  The addition of xanthan gum to guar gum makes the combination more gel-like,  while the addition to pectin stabilizes wheat-protein emulsions. 
Xanthan gum may also be added to konjac glucomannan in order to develop a sustained-release drug delivery system.  Xanthan gum matrix tablets also work better with insoluble drugs over soluble drugs due to the problem of swelling of the polymer matrix.  Indomethacin, an insoluble drug, is released by the mechanism of erosion while caffeine and sodium indomethacin, both soluble drugs, are released by the mechanism of diffusion of the polymer matrix. 
It is also useful in thickening juices and drinks to assist people with dysphagia (a condition where it is difficult to swallow food) to swallow properly.  However, it is required for the beverages to be chilled for several hours (2-4 h) before the rheological (flow) characteristics of xanthan gum can be stabilized. 
Xanthan gum has been shown to be beneficial for those with diabetes or high cholesterol levels. The mechanism of action is mainly through its effectiveness in slowing gastric emptying due to its pH-dependent viscosity. It can also be used as a thickener in beverages, which helps to assist those with dysphagia. Lastly, it can be combined with other gum or gum-like substances to confer additional properties and be used to encase drugs to function as a sustained-release drug delivery system.
Scientific References :
1. PubChem: https://pubchem.ncbi.nlm.nih.gov/compound/47932
2. Use of xanthan gum in dietary management of diabetes mellitus. (Am. J. Clin. Nutr., 42(4), 597–603. doi:10.1093/ajcn/42.4.597)
3. Development of eggless gluten-free rice muffins utilizing black carrot dietary fibre concentrate and xanthan gum. (J. Food Sci. Technol., 53(2), 1269–1278. doi:10.1007/s13197-015-2103-x)
4. The dietary effects of xanthan gum in man. (Food Addit Contam. 1987 Jan-Mar;4(1):17-26. doi:10.1080/02652038709373610)
5. Improved Hypolipidemic Effects of Xanthan Gum-Galactomannan Mixtures in Rats. (Biosci. Biotechnol. Biochem., 64(10), 2165–2171. doi:10.1271/bbb.64.2165)
6. Influence of anionic dietary fibers (xanthan gum and pectin) on oxidative stability and lipid digestibility of wheat protein-stabilized fish oil-in-water emulsion. (Food Res. Int., 74, 131–139. doi:10.1016/j.foodres.2015.04.022)
7. Synergistic interaction between xanthan and guar gum. (Carbohydr. Res., 138(2), 207–213. doi:10.1016/0008-6215(85)85104-1)
8. Viscosity of food gums determined in vitro related to their hypoglycemic actions. (Am. J. Clin. Nutr., 46(1), 72–77. doi:10.1093/ajcn/46.1.72)
9. Viscoelastic properties of xanthangalactomannan mixtures: comparison of guar gum with locust bean gum. (Carbohydr. Polym., 34(3), 165–175. doi:10.1016/s0144-8617(97)00095-7)
10. In vitro evaluations of konjac glucomannan and xanthan gum mixture as the sustained release material of matrix tablet. (Carbohydr. Polym., 73(2), 241–247. doi:10.1016/j.carbpol.2007.11.027)
11. Interaction in Xanthan-Glucomannan Mixtures and the Influence of Electrolyte. (Macromolecules, 27(15), 4204–4211. doi:10.1021/ma00093a023)
12. Xanthan and Glucomannan Mixtures: Synergistic Interactions and Gelation. (Biomacromolecules, 3(3), 498–504. doi:10.1021/bm010163v)
13. Improving the stability of wheat protein-stabilized emulsions: Effect of pectin and xanthan gum addition. (Food Hydrocoll., 43, 377–387. doi:10.1016/j.foodhyd.2014.06.013)
14. The Amount and Distribution of Water, Dry Matter, and Sugars in the Digestive Tract of Rats Fed Xanthan Gum. (Exp. Biol. Med., 172(3), 340–345. doi:10.3181/00379727-172-41567)
15. Swelling and drug release behaviour of xanthan gum matrix tablets. (Int. J. Pharm., 120(1), 63–72. doi:10.1016/0378-5173(94)00410-7)
16. Rheological Characteristics of Cold Thickened Beverages Containing Xanthan Gum–Based Food Thickeners Used for Dysphagia Diets. (J. Acad. Nutr. Diet., 115(1), 106–111. doi:10.1016/j.jand.2014.08.028)
Regulatory References :
1. EU Approved Food Additive 
2. International Fragrance Association Transparency List