what is a bank 1 o2 censor

For your car, it is the oxygen sensor located either on the exhaust manifold or shortly after it, before the catalytic converter. In case you don't know, oxygen sensors measure how lean or rich your engine's fuel mixture is in real time, letting the engine computer know whether it needs to increase or reduce the amount of fuel getting into the engine. They are quite reliable and last a long time, but eventually they fail and need replacement.

so bank one is the one befor the cats? there are 230,000 miles on this car and it just has a hard time getting started. Once you get it started it runs perfect. The diagnostic code said bank 1 O2 censor. Would this cause it to sound like it was flooding out when you are trying to start it?

There is bank 1 and bank 2 depending on the cylinders (this goes for any car) you will either have both or just bank 1. Four cylinder engines (such as yours) only have bank 1. There are however two sensors. Bank 1 Sensor 1 (Before the Cat) and Bank 1 Sensor 2 ( after the cat) On a v6 or v8 engine there will be Bank 1 Sensor 1 and Bank 1 Sensor 2. (Same idea as before but it will relate to one side of the engine. Then Bank 2 Sensor 1 and Bank 2 sensor 2 will be the opposite side of the motor. As for your vehicle, replace the front 02 sensor and you will be good to go. A bad o2 sensor can cause poor starting, bad gas mileage, among many other things.

How do I know which o2 sensor is bad?

Without an engine code?