Can I access the internet anywhere with an iPhone?

[pinkblink1]

If I go on the standard £30 monthly contract to O2 when I buy my iPhone 3GS, does this mean I can access the internet anywhere, or just in wifi areas?
It confuses me because people on twitter, (mostly celebrities!) are always sending photos/twittering via their mobile, but how do they do this when there isn't wireless internet?

[travis bickle]

Yes you can use the internet anywhere, but it costs money I'm pretty sure.

[Roseanne]

There is something called Wi-Fi. It is wireless internet connection. It allows you to use the internet in certain places such as the airports, hotels and some other places. Currently, I only know one way you can get internet and it's only Wi-Fi.

[evilattorney]

The iPhone is enable for both wifi and 3g internet access. However, you may not be able to access the 3g network without O2 online. You need to check to see exactly what your monthly contract encompasses.