Google entered the smartphone market with a markedly more open approach to mobile software than Apple. It now wants the end-user to tap that openness directly, without relying on a third party for simple software needs. App Inventor for Android is intended as a visual application development tool for just about anyone.
According to its official page: “The App Inventor team has created blocks for just about everything you can do with an Android phone, as well as blocks for doing "programming-like" stuff-- blocks to store information, blocks for repeating actions, and blocks to perform actions under certain conditions. There are even blocks to talk to services like Twitter.”