A bead dispenser or a caulking bead gun means that applicator is designed to dispense the adhesive or sealant only in the form of beads. These applicators are supposed to be used while keeping them very close to the substrate.
Of course the bead dispenser can also be used to apply small dots but they cannot be used to dispense fixed quantity of adhesive or sealant as in case of a potting application. Sometimes users try modify bead dispensers (for example Cox Airflow 3 and Cox Airflow 1 Pneumatic Dispensers) to apply fixed quantity of glue per shot. This is not a practically feasible output from a bead dispenser and adhesive quantity after every subsequent shot reduces.