A preservative is a substance added to products, especially food and cosmetics, to prevent spoilage and extend shelf life. They work by inhibiting the growth of bacteria, molds, and yeasts, which can cause food to decay or become unsafe to consume. Common examples of preservatives include sodium benzoate and sorbic acid. Preservatives can be natural or synthetic. Natural preservatives, like salt and vinegar, have been used for centuries, while synthetic options are often more effective at lower concentrations. While they help maintain product quality, some consumers prefer to avoid synthetic preservatives due to health concerns.