It has 3 legs marked 1, 2 (c - for common) and 3 (+/-) for light.
The rocker switch moves a metal arm between contact 2 and 1 on and off.
The 2 (c) is always on, only contact on pin 1 is on / off.
Pin 3 can be connected to the opposite polarity then what you chose to switch so the light turns on.
Note some have a led connected and same have a indicator glass bulb for 220v.
