I have a model of a house which I want to repeat many times. If I make that house as a prefab and duplicate that prefab then will it be counted as mesh or its just a clone of prefab and will not be counted as mesh and there will be only one house mesh.
If it is counted as mesh and doesn't reduce the size of game then what is the difference between duplicating the house mesh and making it as prefab and duplicating that prefab?
It will be an instance of a mesh. Your overall game size won't increase, given that all instances refer to the same fundamental asset.