What happens if i turn off Wi-Fi on my iphone 4?

I'm new to smartphones and i'm not really a tech whiz. I'm just wondering what happens if i turn off the Wi-Fi when i leave the house. Does it use3g and just connect to any network and use up my allowed megabytes or would it not do anything?

If you switch it off, your phone won't be connected to Wi-Fi. It depends if your data services are on. If they're on, it'll use up your allowed MB.

Your 3G or 4G will turn on.

Is that all? Then why do you have to have Wi-Fi for your petsonal hotspot to work?

Is that all? Then why do you have to have Wi-Fi for your petsonal hotspot to work?