IPhone 4: Does using your wifi count as data?

I'm using my iPhone and I have my wifi on. If I'm online, is that just using the wifi or is that counting towards my data usage?

No it will bypass your data usage.

No, if your using WiFi it does not affect your data.

No it will not I promise! :)

Data passes by two methods. Over the cellular network on 3G or over WiFi. The dataplan is tied to 3G usage. If you are using WiFi you are not using up your data plan usage.

No its not. Only 3G/4G does.