The screw terminal is commonly used to provide a secure electrical contact with larger PAR lamps. Typically the terminal has two screws, though 3-screw terminals are also fairly common.
Larger PAR lamps are generally used in applications such as stage lighting, swimming pool lighting and floodlighting, amongst others.
ST2 (2-screw terminal), ST3 (3-screw terminal).
PAR 36, PAR 38, PAR 46, PAR 56, PAR 64.