What is iOS 7 supposed to do?

Will it be like a software update for all the iphones and ipads?
Does it mean you have to buy a new phone with this software?
Does it cost?

The Software is free, it will come out on September 10th and it basically changes your iphone and you can update it in Settings>General>Software Update then tap on it and it will update.
Ps you will not have to buy a new phone.

1: Yes, but the new interface looks like a joke.

2: No

3: No, but I estimate it will be the worst update to come out of Apple for awhile. I'm still on iOS 5 right now.

You can see some of the features here…

http://www.apple.com/.../ios/ios7/

It will be a fee update but it will not work on some older devices.

It works with iPhone 4 or newer

iPod Touch 5th generation

iPad 2 or newer

iPad Mini

IOS 7 will be free and work with IPhone 4 and newer, and with IPad 2 and newer.
Unless you have old apple product your will be able to freely update to IOS 7 by going to Settings->General->Software Update on your apple product at IOS 7 release on the 10th of September 2013.

1. Yes, iOS 7 will be a software update for iPhones, iPads, and iPod touches. Just like any other version of iOS (iOS 4, iOS 5, iOS 6) that might be installed on your Apple iDevice. It will be available sometime in September, presumably the 10th. Just like any other software update, to update you must go to your settings app, then general, and then software update. Here, it will ask you If you want to upgrade to iOS 7. Of course, you will have to wait until it is officially released to the public to upgrade.

2. Well that depends on the device you are talking about. The iPad 2nd generation, iPad 3rd generation, iPad 4th generation, and the iPad mini, will be capable of running it. Any versions of the iPad below those I have listed (such as the first generation iPad) will not be able run it and you will have to upgrade to the iPads I have listed.
The iPhone 4, iPhone 4S, and iPhone 5 will be able to run iOS 7. Any version if the iPhone below the ones I have listed do not support iOS 7 (say for example, the iPhone 3GS)
If you were thinking of the iPod touch, then the only version of the iPod Touch that will be capable of running iOS 7 is the iPod touch 5th generation. Anything below that will not support it.

3.No. Just like previous versions of iOS, this will be free of charge once it comes out in September. If you are willing to try iOS 7 beta versions (the "testing" versions of iOS that are for developers only) ahead of when it comes out to the public, you would have to pay $99 US Dollars for a developer account to try out iOS 7 beta versions. The beta versions are not recommended If you're just going to play with it, but are only for people who want to help Apple improve iOS 7 with bugs in the stock apps, user interface, etc. (but not with 3rd party apps like Facebook, twitter, etc. Because those apps are not owned and operated by Apple)

All their OS's are free upgrades.