A sconce is a type of light fixture

Lighting

Lighting or illumination is the deliberate application of light to achieve some practical or aesthetic effect. Lighting includes the use of both artificial light sources such as lamps and light fixtures, as well as natural illumination by capturing daylight...

 affixed to a wall in such a way that it uses only the wall for support, and the light is usually directed upwards. It does not have a base on the ground. The word applies both to traditional forms of torch

Torch

A torch is a fire source, usually a rod-shaped piece of wood with a rag soaked in pitch and/or some other flammable material wrapped around one end. Torches were often supported in sconces by brackets high up on walls, to throw light over corridors in stone structures such as castles or crypts...

 lighting, but also to modern gas

Gas lighting

Gas lighting is production of artificial light from combustion of a gaseous fuel, including hydrogen, methane, carbon monoxide, propane, butane, acetylene, ethylene, or natural gas. Before electricity became sufficiently widespread and economical to allow for general public use, gas was the most...

 and electric light

Electric light

Electric lights are a convenient and economic form of artificial lighting which provide increased comfort, safety and efficiency. Most electric lighting is powered by centrally-generated electric power, but lighting may also be powered by mobile or standby electric generators or battery systems...

 sources affixed in the same way.

The etymology of sconce is from the Latin absconsus, and the French esconce. It is a word of many meanings, mostly signifying a covering or protection, or, by extension, that which is covered or protected.

Modern electric light

Electric light

Electric lights are a convenient and economic form of artificial lighting which provide increased comfort, safety and efficiency. Most electric lighting is powered by centrally-generated electric power, but lighting may also be powered by mobile or standby electric generators or battery systems...

fixture sconces are often used in hallways or corridors to provide both lighting and a point of interest in a long passage. Sconce height in a passageway is generally 3/4 of the distance up the wall as measured from the floor to the ceiling, and the distance between sconces on the wall is generally equal to the distance of the sconces from the floor, often alternating sides of the passageway.