We all know that water is an enemy of fire. There is a fire triangle made up of heat, fuel and oxygen. For a noramal fire to burn, all these elements have to be present. if any of these is absent, fire will not occur. This is where water plays the trick.
Water puts out fire in two ways. When we spray water on fire, it takes some heat away from the fire and gets itself evaporated. When water takes away heat, the temparature thus falls below the levels of burning. so, fire goes out. if we use a lot of water, fire is extinguished by cutting off the oxygen supply too. Here, water acts as a layer between air and fire.
But, we can't use water for dousing all types of fire. Don't apply water to such types of fire as electrical fire and oil fire.