It probably means that if you have MIL eliminators, than one has gone bad or if you don't then it's just telling you that you have no cats. If your h-pipe has high flow cats it can still sometimes set off those codes.
The problem is that my car is running bad, it originally didnt throw any Check Engine Codes, and then a day after it running bad it popped the check engine light on. That is the code that came up. Would an o2 sensor cause my car to run bad?