Android is an open source platform developed by Google and the Open Handset Alliance for mobile devices. It consists of an operating system, middleware, and key applications. The document provides an overview of Android versions from 1.1 to 4.1 Jelly Bean and their market shares. It also discusses installing the Android Development Tools plugin for Eclipse, exploring a sample project's components, and developing applications considering different Android versions. The sample project demonstrates creating layouts, handling button clicks, launching a new activity, and registering activities in the manifest file.