I want to wire in the following thermostat.
https://proax.ca/en/product/205417/RIT3110000 

And am having a hard time understanding the wiring diagram
[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/Nn1S3.png

I think I get that 5 is L and can be connected to your heater (3) or cooling (4). So pins 3,4,5 are just a single pole double throw switch? I would be able to connect 24V to pin 5 and probe pins 3 and 4 to determine if the thermostat was above/below the set point? Or does the switch need power and is that incorrect?

Maybe instead pin 5 needs to be 120VAC or 240VAC depending on location, and then what would 1 and 2 be?

I'm missing something - any help would be greatly appreciated!