The S stands for speed, and the 3G stands for the third generation, HSPA (High Speed Packet Access – wikipedia link) data network, which is also supposed to bring broadband-like speed to your iPhone’s internet connection. When you’re on the 3G network, you can tell by the little 3G symbol at the top of left of your iPhone’s menu, right beside the signal strength bars and the name of your carrier (AT&T, Rogers, O2, Orange, etc.).

There are several other symbols your iPhone might show instead of 3G, however, depending on the type of connection and reception available in your area and sometimes specific spot.

If you don’t have a 3G connection, whether your area doesn’t support it or you’re just indoors or behind an obstruction that’s preventing it, your iPhone might default down to a 2G connection, known as EDGE, (Enhanced Data rates for GSM Evolution – Wikipedia link). That’s the little E symbol, and If we keep the same analogy, this is older, slower technology — dial-up to 3G’s broadband.

If you’re getting an E and you really think you should be getting 3G, try going to the Settings Icon and toggling Airplane Mode on and off. That should force your iPhone to re-connect with the network and give you the fastest speed available. Sometimes even moving to a different, less obstructed spot can make a big difference.

If even EDGE isn’t available, the iPhone will still try to connect via GPRS (General Packet Radio System – Wikipedia link) an even older, slower 2G protocol shown with an O symbol (for outside chance?). To stretch our analogy as thin as this signal, GRPS would be the ancient 24K modems.

Of course, if you have Wi-Fi enabled and connected, you’ll get the Wi-Fi fan symbol instead.

If you’ve turned all the radios off and gone into “Airplane Mode”, you’ll get the little airplane symbol and absolutely no connection to the internet whatsoever. (Turn Airplane Mode off — and your connections back on — via the Settings icon on your home screen.)

And yes, you can turn on Airplane Mode and still re-enable Wi-Fi if you really want to.

We told you when iPhone 2.0.1 dropped, we asked you how 2.0.1 was doing for you? And we warned iPwners to stay away. Turns out people running on Vodafone (in the 10 countries they currently supply) might want to consider staying away for now as well. TUAW reports on the problems:

Specifically, users who paid to have their 3G iPhones unlocked by Vodafone* are unable to re-connect to the service following the update, and instead receive a “0xE8000001″ error message. How helpful. It seems to happen on both Windows and Mac OS X.

Another problem, via iPhoneAtlas, occurs when users try to upgrade when in the radio-silent Airplane Mode:

Having Airplane mode turned on can result in a non-functional phone when the update is applied. You may receive the error message: “Information for activation cannot be obtained from the iPhone” Fortunately, you can disable Airplane mode from the emergency screen if your iPhone is put into an inactivated state by a problematic update.

If you do get 2.0.1 installed (and I confess, mine installed quickly and flawlessly), what will you find under the hood?

Apple said “bug fixes”, which seems to include fixes to sluggish interface animations/transitions and app launches in general (especially Contacts and SMS). Some are claiming faster backups, more stable App Store app behavior, and better or more accurate cell strength and GPS placement. And others have even joked that, like a placebo, we’ll see any update as a general purpose cure-all for what’s been aggravating us.

Have you noticed any specific, repeatable improvements? Keep pounding away and let us know what you find!