Thermostats keep your home at even temperature throughout. Individual room temperature may vary and be regulated by adjusting registers in various rooms. The temperature may also vary between floors as warm air rises. If you have a second floor, it is likely to be warmer than a lower level. If your home has zoned heating and cooling you may have a thermastat on each floor to help manage temperatures.
Registers throughout your home help to regulate the flow of air and to maintain the desired temperature. By opening and closing the registers you can determine the amount of cool or warm air that enters a room. This combined with the thermosts will help maintain the temperature in your home. In addition to registers that output air, your home will have return registers. None of these registers should be obstructed.
You system has an air filter to help keep the air in your home clean. These should be replaced regularly. Clogged fileters can cause a unit to malfunction. Refer to manuals for your system to locate the filters and how to clean and replace it.