IPhone 3 Application requires ios

I have iPhone 3 and i'm going to install an app and it says: Requires iOs 4, 3 or iOs 5 what's this? Can i downlaod it or what?

Some newer apps require newer versions of iOS which is the basic operating system software in the iPhone. Older iPhones can't be upgraded to the newest version of iOS. To see what your phone *can* be upgraded to (if anything), go to Settings > General > Software Update.

Nope you can't download those apps iPhone 3G can only go up to iOS 4.2.1

This is happening a lot recently. The iPhone 3 is pretty much unsupported now days and most app developers are aiming the apps at the newest firmware. Your going to find that before long most apps will fail to work on your iPhone 3 and your going to be forced to upgrade to a newer model.

Your only other option is to try "jailbreaking" your phone and searching around for the older version of the app and then installing using a program like iFile or funbox. ( iFile and funbox will only do the job once you are jailbroken ). Most can easily be found with by spending a few minutes on google but as for most apps on the app store you will need to be running IOS 4.3 or above

IOs is the mobile operating system iPhones, iPads & iPod Touches run on. 4.3 is a firmware version just like 5.0 but unfortunately your 3G (second gen iPhone) only runs up to to iOS 4.2.1, so you can't download that specific version of that app. So jailbreak your iPhone & try & find an older version of that app.

There's no iPhone 3.In this case it is the 3G. You can't download it on this model. You'd have to get a 3GS at least to get iOS 6.1.3 which is the latest, though I'd recommend the 4S if at all possible because the 3GS is no longer made & the 4 will also no longer be made when the next iPhone is announced, later this year.