A bed side sconce is a light mounted on the wall beside a bed. That is it at the most basic level.
Instead of placing a lamp on your nightstand, the light lives on the wall. This frees up surface space for books, a phone, or just a little breathing room. In smaller bedrooms, that extra space can make a big difference.
Functionally, it works like a bedside lamp. You use it for reading, winding down, or getting up in the middle of the night without turning on the main ceiling light. Some bed side sconces are fixed in place and cast a steady glow downward. Others have adjustable arms so you can bring the light closer to the page.
Height matters. The fixture is usually installed around shoulder or eye level when you are sitting up in bed. That way, the light hits the book and not directly in your eyes.
It is a practical choice, especially if you like a cleaner look or want to avoid visible cords.
Light where you need it. Nothing extra.