When searching for an oxygen sensor for your vehicle, you may be asked to choose if your vehicle has "CARB" or "California Emissions Standards" vs. "Non-CARB" or "Federal Emissions Standards". This is not associated with where the vehicle is driven or where it was purchased, but rather the standards to which the vehicle was manufactured.
There are two authorities regulating vehicle emissions: U.S. Environmental Protection Agency (EPA), which governs the country's Federal law, and the California Air Resources Board (CARB), which governs emissions laws in California and additional states that follow California emissions laws. Therefore, even if you're not located in California, you may have a California emissions-equipped car. If your vehicle was manufactured to California emissions, the exhaust configuration and actual components used may be different than a vehicle manufactured to Federal emissions.
You can identify a CA or Federal vehicle by the emissions system label. Try looking in the door jamb, on the front radiator support, strut tower plate, or under the engine hood. The label will say something along the lines of "This vehicle conforms to...regulations applicable to...". If "This vehicle conforms to..." mentions California, the vehicle was manufactured to CARB standards and you'll need to purchase the CARB/California parts. If "This vehicle conforms to..." does not mention California, the vehicle was manufactured to Federal EPA standards and you'll want to purchase the Federal/Non-CARB/Non-California parts. Using the incorrect part will prevent your car from operating properly, turning on the check-engine light and creating other problems.