Fence is a wall like structure but it is not a wall. A wall is generally needed to avoid passage and viewing of the other side. But a fence allows the sighting of the other side. It only restricts the movement from one side of the fence to other side.
The fence structure is used for agricultural purposes. There it is used to protect the crops from animals which are threatening for the crop. Fences are also used to provide privacy fencing for the purpose of some privacy. During construction of buildings and other structures, fences are often temporarily made to provide safety from falling to the ground during the construction work. Security fencing is for providing security for house from thefts and trespassers or animals. A decorative fence gives beauty to the sight of a garden indoors or outdoors. Even a landscape gets a good appearance with decorative fences.
In some countries the height of fences is limited. A special permission from the local authorities will required to maintain high fences. Generally only government organizations related to defense or most sensitive things are secured with high fences.
There is a quote by Dudley Nichols saying that the fear is the highest fence of all. Robert Frost in his poem, ?Mending Wall?, mentions that good fences can make good neighbors.