There are thousands of apps in Apple's iTunes app store that bring extra functionality to the iPhone. But unlike handsets that run Google's Android open-source platform which allows users to download apps from third-party stores, Apple smartphones owners can only install software available through the app store and approved by Apple.
However, if you 'jailbreak' your smartphone you can run and install third-party apps not available from the iTunes app store. 'Jailbreaking' simply mean installing a program that removes restrictions in the default software so you can run other apps.
Although it's worth noting, jailbreaking your handset does run a small risk of bricking your phone, rendering it unusable. So think carefully before you go ahead with this and don't say we didn't warn you. Furthermore, it will void the warranty on the Apple smartphone and there's no guarentee the apps you download haven't been inefcted with malware, as has been the case for some Google Android apps.
Lastly, remember to back-up your handset in iTunes so that if any problems occur you can restore the iPhone to its original state.
Here's how to jailbreak an iPhone running iOS 4.3.3.
From the Home screen open Safari (the web browser) and then Visit the JailbreakMe website.
From the page displayed, press the Free button and then select Install.
Now press the Jailbreak button and the Cydia app will be installed. If successful, a message will be displayed alerting you to the fact the installtion has finished.
From the home screen select the Cydia app and now you can browse and install whatever third-party apps you want.