This is a BRAND NEW-In-The-BOX White Rodgers relay with a 24 volt coil. It has two completely independant circuits with a "Normally Open" set of contacts and a "Normally Closed" set of contacts. The bottom two prongs are the 24 volt coil the top 2 prongs are for the Normally Open circuit the the middle two are for the Normally Closed Circuit. They are rated "Heavy Duty" and can handle 10+ Amps . Thanks for looking and good luck!
Relays are switches that open and close circuits electrically. In most HVAC equipment a low voltage coil relay (24 vac) is energized in order to open or close a higher voltage (usually 120-240) circuit.