Android - a definition

Android is a software platform for mobile devices that includes an operating system, middleware and key applications supported by Google.
Everybody can develop applications on the Android platform using the Java programming language and Android SDK.

Features

• Application framework enabling reuse and replacement of components
• Dalvik virtual machine optimized for mobile devices
• Optimized graphics powered by a custom 2D graphics library; 3D graphics based on the OpenGL ES 1.0 specification (hardware acceleration optional)
• SQLite for structured data storage
• Media support for common audio, video, and still image formats (MPEG4, H.264, MP3, AAC, AMR, JPG, PNG, GIF)
• GSM Telephony (hardware dependent)
• Bluetooth, EDGE, 3G, and WiFi (hardware dependent)
• Camera, GPS, compass, and accelerometer (hardware dependent)
• Rich development environment including a device emulator, tools for debugging, memory and performance profiling, and a plugin for the Eclipse IDE

Android includes a set of core libraries that provides most of the functionality available in the core libraries of the Java programming language. Every Android application runs in its own process, with its own instance of the Dalvik virtual machine. The Dalvik VM relies on the Linux kernel for underlying functionality such as threading and low-level memory management. Android relies on Linux version 2.6 for core system services such as security, memory management, process management, network stack, and driver model.

Source: http://code.google.com/android/what-is-android.html