Like a person goes into Android Programming and wants the app to work on iOS for Apple.
Are they the same or different?
Depending on what you wish to do, you might make use of technologies like PhoneGap or Titanium Appcelerator to write a single program that works on both iOS or Android.
As RubberMan pointed out, these two platforms have applications that are built using a different technology stack, but for high-performance applications like games, you'll probably end up using C++.
For more generic applications (think most productivity apps, foto sharing apps etc.) you might wish to invest the time and effort to build native applications if you use a lot of device services and need lots of performance. If you have something that just displays some information or is a data capturing program, you can get by with a hybrid application.
Thanks for the info.
If you would like to develop for cross platfrom, I would recommend visualwebgui for cross platform development and for native-like development. Yo ucan take a look and see if it meets your requirements for creating a messaging application. To answer your concern, you will not need a Mac for this as it is HTML5 and not specifically for iOS and Android. This is a good alternative as you do not need to learn a specific skillset or focus on a specific platform. Rather, it allows you to build HTML5 business apps with native quality user experience in C# using a visual designer. If you're interested you can read more at http://www.gizmox.com/products/visual-web-gui/
Edited by happygeek: Spam (infraction reversed - but please note that you cannot just reply to everything with the same cut and paste product promoting message)