Flames are visible, glowing gases produced by the combustion of materials, such as wood or gasoline. When a substance burns, it releases heat and light, creating a flame that can vary in color and intensity depending on the material and temperature. The process of combustion requires oxygen, which is why flames are often seen in the presence of air. The color of a flame can indicate its temperature and the type of fuel being burned. For example, a blue flame typically signifies complete combustion, while a yellow flame may indicate incomplete combustion, producing soot. Flames are commonly used for cooking, heating, and in various industrial processes.