Do you have an older gas furnace built into the wall or the floor? Make sure you don’t have a millivolt heating system. These systems are common in older homes and don’t work with Nest Thermostats.
If you don't, then it's likely compatible with the Nest Learning Thermostat or Nest Thermostat E (but not the Nest Thermostat 2020 model).
One other point to note is Nest thermostats generally work without a common ("C") wire. However, some systems require one, or the Nest Power Connector if the thermostat doesn't get enough power from your thermostat wires.
