Foam is a substance formed by trapping pockets of gas in a liquid or solid. It is commonly seen in everyday items like shaving cream, whipped cream, and bath foam. The bubbles in foam are created when air is mixed with a liquid, causing it to expand and create a light, airy texture. Foam can be classified into different types, such as polyurethane foam used in mattresses and cushions, or styrofoam, which is often used for packaging and insulation. Its unique properties make foam useful in various applications, from construction to food preparation.