Food additives are substances added to food to modify or enhance properties such as appearance, flavor, texture, or shelf life. They're used most heavily in processed and packaged foods, though some appear in fresh or minimally processed foods too.
Additives can be derived from natural sources such as minerals, plants, or animals, or produced synthetically. Common categories include preservatives (such as sodium benzoate, potassium sorbate, and sulfites, which inhibit bacteria, mold, and yeast), colorants, flavorings, emulsifiers (such as lecithin and polysorbates, which keep ingredients from separating), thickeners (such as gums and starches), and sweeteners.
In most countries, additives are regulated by food safety agencies (such as the FDA in the US or EFSA in the EU) and must be tested and approved before use in food products.
Additives are generally considered safe when used within regulated limits, though ongoing research into long-term health effects has driven consumer demand for "clean label" foods with fewer or more recognizable additives.