What do the wires mean on a thermostat?

Rh stands for Red-Heat and Rc stands for Red-Cool. If you only have a single red wire the jumper between Rh and Rc are required for some heating and cooling hybrid systems depending on your thermostat. Yellow/Y is the AC compressor. White/W is the Heating element. Green/G runs the fan.

What are the 2 wires on a thermostat?

The most basic thermostat has 2 wires; usually a red and a white wire. Two wire thermostat wiring is used for furnaces only and usually doesnt need a “C” or “Common” wire. Thats why we only need two wires: Red wire for power (24h).