Sodium selenite is a colorless, crystalline solid and a key source of the essential trace element selenium. Highly soluble in water, it's widely used as a feed additive to prevent selenium deficiency in livestock, supporting immune function and reproductive health. In the glass industry, it functions as a decolorizing agent, neutralizing the green tint caused by iron impurities. It is also used in medical and research applications for its potential antioxidant and anticancer properties.

Sodium selenate is a white, water-soluble inorganic salt of selenium. A significant application is the bio-fortification of crops, where it is used to increase the selenium content in food and feed, addressing widespread deficiencies. Similar to selenite, it is also used as a decolorizing agent in glass manufacturing. In agriculture, it can serve as an insecticide to control pests like aphids. It's also found in some dietary supplements due to its high solubility.