The ones you used Inventor app to build android applications you will surely know something of its history. It is a system, originally provided by Google and currently maintained by MIT (it was created by MIT Professor Harold Abelson, in 2009), which allows you to create applications without the need for extensive programming knowledge. It was used in various educational centers before going to market, uses visual programming, dragging blocks, and was no longer considered a product of Google in August 2011, when the code began to be free code.
Available at appinventor.mit.edu now they have a new version that can be run from the browser (less from Internet explorer, although they are working so that it can also be supported), being possible to install an emulator to test the applications created without the need to have an android device.
There are several inventor app courses on the Internet, this being one of my favorites (est en portugus). On YouTube there are dozens of excellent videos showing how you can make applications by dragging and dropping blocks of information, ideal for understanding the basics of programming without digging into the code. On its main page there are also several tutorials to get started with the system.
The first version of App Inventor is still available, although they will stop supporting during 2014.