Bead sights are quick target acquisition
sights which are mostly used for point shooting
. It is most often used in shotguns
or similar scatterguns
The bead sight is usually a highly polished bead of gold or silver colored material and is put in place of a front sight. There usually is no rear sight on shotguns that use a bead sight.
You basically point the long arm at whatever you want to hit and once the bead is more or less centered at your target and is somehow aligned with the rear part of the shotgun you just squeeze the trigger and see the target get blown to bits.
It makes target acquisition faster as there are fewer planes of vision you will have to align.
Point shooting does not make for terribly pinpoint accurate shooting but makes it fast and easy to hit even moving targets.