1. Drug / Medicine – Used to treat, alleviate, cure or prevent sickness. As officially declared by a governmental drug/medicine regulatory body
2. Gelling Agent / Thickener – Increases the viscosity by thickening the liquid to give it more texture
3. Humectant – Binds with water to increase skin hydration. Also enhances water absorption of the skin
Sodium Hyaluronate is the salt form of Hyaluronic Acid, a water-binding ingredient that has the ability to fill the spaces between the connective fibers known as collagen and elastin. Hyaluronic Acid is often injected into the skin (on the face most often), and hydrates and separates the skin, allowing it to retain water and create a plumping effect. Sodium Hyaluronate has been used for moisturization and wound healing. Because the skin naturally loses its water composition as it ages (going from 10% – 20% water to less than 10%), Hyaluronic Acid and Sodium Hyaluronate can replace some of the water lost in the dermis, and potentially fight wrinkles and other signs of aging.
Sodium Hyaluronate is derived from rooster comb or by the fermentation of yeast, and applied topically, forms “an air permeable layer and penetrates into the dermis, thus boosting the elasticity and hydration of the skin” (BioChemicals, a producer and retailer of Sodium Hyaluronate for cosmetic formulas). It has the ability to adjust its moisture absorption based on the relative humidity in the air, as well as protect the skin by scavenging for reactive oxygen species created by UV rays, fighting sunspots and other age spots. The small molecules can penetrate deep into the dermis, maintaining and attracting water, as well as to promoting microcirculation. 
Recent Findings :
Hyaluronic acid and its salts, sodium hyaluronate and potassium hyaluronate are commonly used in cosmetics as skin conditioning agents. It is not immunogenic, not a sensitizer, not a genotoxic nor does it show any kind of carcinogenicity. However, an “increased expression in hyaluronic acid genes may be a consequence of metastatic growth” which means that hyaluronic acid and its salts can be used as a cancer indicator. 
Sodium hyaluronate is used as a cosmetic humectant or thickener. Both sodium hyaluronate (HA) and the research team’s novel invention, sodium acetylhyaluronate (AcHA), have a maximum bound water content of 0.89 g of water per g of humectant. “The skin softening effect of humectants depends on their water-holding capacities; hence the higher the water-holding capacity, the more the skin-softening effect”  Another study also showed that if hyaluronic acid was presented in a “crosslinked resilient HA (RHA)” form, there is a 7.6% increase in epidermal water content over the control.  Crosslinking is the formation of chemical links between molecules to form a more stable, structured polymer.
Latanoprost is used to treat increased pressure in the eye, and the addition of sodium hyaluronate alleviates the side-effects of Latanoprost by reducing ocular surface toxicity.  Sodium hyaluronate has been used to prevent endothelial cell loss during intraocular lens implantation (an artificial replacement for the lens of your eye) since the 1980s. 
Sodium hyaluronate is used cosmetically as a humectant or thickener. Its main pharmaceutical use is to prevent damage to the eyes.
Scientific References :
1. PubChem: https://pubchem.ncbi.nlm.nih.gov/compound/3084049
2. Final Report of the Safety Assessment of Hyaluronic Acid, Potassium Hyaluronate, and Sodium Hyaluronate (Int. J. Toxicol., 28(4), 5–67 DOI:10.1177/1091581809337738)
3. Differential scanning calorimetry studies on the mechanism of skin-softening effect of sodium acetylhyaluronate (Polym. J., 41(16), 6055–6059. DOI:10.1016/s0032-3861(99)00852-6)
4. Pilot Comparative Study of the Topical Action of a Novel, Crosslinked Resilient Hyaluronic Acid on Skin Hydration and Barrier Function in a Dynamic, Three-Dimensional Human Explant Model (J Drugs Dermatol. 2016 Apr;15(4):434-41)
5. Sodium Hyaluronate Decreases Ocular Surface Toxicity Induced by Benzalkonium Chloride–Preserved Latanoprost: An In Vivo Study (Investig. Ophthalmol. Vis. Sci., 54(5), 3385. DOI:10.1167/iovs.12-11181)
6. The Effects of Sodium Hyaluronate, Chondroitin Sulfate, and Methylcellulose on the Corneal Endothelium and Intraocular Pressure. (Am. J. Ophthalmol., 95(3), 332–341. DOI:10.1016/s0002-9394(14)78301-1)