A "compound" is a substance made up of two or more different elements that are chemically bonded together. For example, water is a compound formed from two hydrogen atoms and one oxygen atom. Compounds can have unique properties that are different from the individual elements that make them up, like how salt (sodium chloride) tastes very different from sodium or chlorine alone. In everyday life, we encounter many compounds, such as carbon dioxide, which is produced when we breathe out. Compounds are essential in various fields, including chemistry, biology, and medicine, as they help us understand how different substances interact and react with each other.