"iOS Application Programming Guide" and "iOS App Programming Guide"

Is there any difference between these two documents?

I found that the document "iOS App Programming Guide" is brand new, and "iOS Application Programming Guide" was last updated at 2010.

So is the document "iOS Application Programming Guide" is replaced by "iOS App Programming Guide"?

But I also found that the contents of two document is obviously different. Any one has any idea of that?

It looks like the first document you listed is the most current, but the best place to keep up to date with the latest news and documents, is the iOS developer network.

https://developer.apple.com/devcenter/ios/index.action

And the latest app developer guide is this one here.

https://developer.apple.com/library/ios/#documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40007072

And another good resource if your starting out as a beginner, is the Stanford University iPhone app developer classes, available on the iTunes store, and there also free to download, I've not used them myself but they do have a good reputation.

Also these two books listed below are the best I've come across for learning the subject from scratch.

Amazon.com: Objective-C Programming: The Big Nerd Ranch Guide (Big Nerd Ranch Guides) (9780321706287): Aaron Hillegass: Books

http://www.amazon.com/iOS-Programming-Ranch-Edition-Guides/dp/0321821521/ref=sr_1_1?s=books&ie=UTF8&qid=1338327046&sr=1-1

Regards Masrk