Furniture is everything that is in a house
There is no clear definition, but rudely, the contents are everything that is in a building (house, barn) and not attached to the building (so if it can be removed without demolition, it is the furniture). The problem in the definition is that wallpaper and tiling is also covered by household furniture, while there is still a demolition work. You will be dealing with the contents when you have a house and you will close a household insurance. You can insure yourself for theft and damage to the contents.