Single-stage heating means the furnace has one level of heat output. An example would be if you only have a gas or forced air heater or if you have an electric AC system, and then a separate heating system. A single stage system is the most common type of system, and it's common all over the country.
Generally 6 wires or less are used in single stage systems. Single stage digital programmable thermostats will give you the most control over your home environment.