I have a iphone and do I need Wi-Fi?

I'm not sure if I need mobile Wi-Fi I'm not sure I'm confused Help!

You don't need it. How much is on your data plan? Just don't go over your allowed data and you won't have extra charges on you bill. So you don't need Wi-Fi.

I'm assuming you're fairly new to this whole iPhone thing so here is how internet basically works on it (Also I'm assuming you bought your iPhone with a plan):

There are 2 ways to access the internet with an iPhone-through wi-fi or through 3g/4g (depending if you have an iPhone 5 or not)
If you are at our house or in a free wi-fi zone most people use the wi-fi because it is generally faster and it doesn't take up data.
If you can't access wi-fi from where you are located, your phone will automatically use 3g/4g to acess the internet.

To answer your question directly, an iPhone doesn't need wi-fi to connect to the internet, as long as you have bought your iPhone with a plan (a contract with Verizon, AT&T, or T-Mobile).

In the off chance that you have bought your iPhone unlocked (Without a plan) the wi-fi is neccesary in order to connect to the internet.

Hope this helps! Any questions about my answer feel free to ask!

Your plan should include data, Wi-Fi is to use when available, to avoid going over your data limit. When you connect it to Wi-Fi you run off of that network as opposed to the one provided through your carrier on your plan.