Foams are materials that consist of a gas dispersed in a liquid or solid. They are created when gas bubbles are trapped in a liquid or solid matrix, resulting in a lightweight structure. Common examples of foams include whipped cream, shaving cream, and polyurethane foam, which is often used in mattresses and cushions. Foams can be classified into two main types: open-cell and closed-cell. Open-cell foams have interconnected bubbles, allowing air and moisture to pass through, while closed-cell foams have sealed bubbles, providing better insulation and water resistance. These properties make foams useful in various applications, from packaging to construction.