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 power wires on a thermostat?

The wires that provide the source of power are the R wires (or hot wires). They are labeled Rh (for heating), Rc (for cooling), or Rh/c (for both heating and cooling). Some thermostats simply have one wire labeled R. The power from the R wire isnt continuous and that is where the C wire comes in.