Dimmer lamp socket with high-low-off positions allows regular light bulbs to operate with 2 levels of light like 3-way bulbs. Standard dimmer sockets have solid brass shells and caps with set screw. Tapped 1/8 IP, dimmer sockets fit standard lamp pipe.
Before making any changes to electrical fixtures and lamps:
Disconnect plug/wire from the electrical source.
Turning lamp off will not protect you from electric shock.
If you are unsure how to safely proceed contact a licensed electrician.