The flash point is the lowest temperature at which a liquid gives off enough vapors to form an ignitable mixture with air.
Manufacturers and the National Fire Protection Association (NFPA) use the flash point to ascertain a liquid's flammability. You can use the flash point to determine the volatility of the flammable liquid. For example, gasoline is very volatile, and fuel oil is much more difficult to ignite.
A flammable liquid is a liquid with a flash point below 100oF (38oC). A combustible liquid is a liquid with a flash point at or above 100oF (38oC).