65 Oxygen Sensor Heater (Secondary) Malfunctioning or defective oxygen sensor heater

What is the oxygen sensor heater? I know my 2nd o2 sensor is broke im just wondering is that why im throwing a 65, or if that is for a differnt reason then just that my o2 sensor is broke.

On a seperate note. When i go to replace my o2 sensor do i get one for a 01 Integra GSR since i have a gsr swap or do i just get one for an 00 civic. Or are they all the same? Any info would be greatly appreciated.

Thanks,
Matt