i just wanna add a bunch of apps and stuff to my iphone. i know with jailbreaking you can install more apps and stuff but what does unlocking it do?
when you unlock, it means that you can use any sim card in it - unlocking doesnt have any effect on apps.
with jailbreaking, you can access everything on the iphone and change settings, like the colour scheme, wallpapers etc.
try looking at the App store on iTunes. there are free apps, or ones that are only a few dollars. good luck!
Apple sells its brainchild: the iPhone locked with certain wireless carriers such as AT&T (although I heard iPhone 3G is sold unlocked in Hong Kong!), so "unlocking" iPhone means you can then use your iPhone with any wireless carriers you wish.
Apple limits the installation of 3rd party software and apps into the iPhone only through its App Store, which you can access it if your iPhone's firmware is or above v2.0. So far, there are plenty of free and paid apps available in App Store. But the most useful ones such as Podcaster and NetShare is not available there, these kinda apps are sold outside the App Store.
Meaning you'll need to 'jailbreak' you iPhone in order to install illegal apps, 'jailbreaking' means you'll lose your iPhone's official waranty.
To 'jailbreak' your iPhone, you can download Win Pwn (URL link is down below of my answer). This is if your computer's OS is Windows...
For more informations about Podcaster & NetShare apps, visit the URL link below too.
Unlocking means that you can use any SIM card in the world in the iPhone/iPhone 3G, any GSM phone in the world.
Jailbreaking means that you break the original code set by Apple, essentially making the phone do things that it originally wasn't meant to. An example of this is jailbreaking an iPhone 3G & installing a video recorder (which is not one of the original features of the iPhone's camera).