A fire blanket is a safety device designed to extinguish incipient (starting) fires. It consists of a sheet of fire retardant material which is placed over a fire in order to smother it.
Fire blankets, along with fire extinguishers, are fire safety items that can be useful in case of a fire.  Due to its simplicity, a fire blanket may be more helpful for someone who is inexperienced with fire extinguishers.