Android is an open-source software stack for mobile phones and similar devices. The Android Open Source Project is tasked with maintaining current and developing new versions of the Android software. We believe that users deserve to have the source code to the software they run on their devices, that developers deserve an open, level playing field for their apps, and that OEMs and carriers deserve the freedom to differentiate and innovate. That's why we created Android, and made the source code open.
Android was originated by a group of companies known as the Open Handset Alliance, led by Google. Today, many companies -- both original members of the OHA and others -- have invested heavily in Android, typically in the form of allocating significant engineering resources to improve Android and bring Android devices to Market.
We created Android in response to our own experiences launching mobile apps. We wanted to make sure that there would always be an open platform available for carriers, OEMs, and developers to use to make their innovative ideas a reality. We wanted to make sure that there was no central point of failure, where one industry player could restrict or control the innovations of any other. The solution we chose was an open and open-source platform.
But the ultimate goal, of course, is to improve the mobile experience for real users by facilitating innovation. Accordingly, the primary goal of the AOSP is to make sure Android is a success as an end user product.
The companies that have invested in Android have done so on its merits, because we collectively believe that an open platform is necessary. In some ways, Android is the purest form of an open-source (as opposed to free software) effort: a group of organizations with shared needs has pooled resources to collaborate on a single implementation of a shared product. That is, the Android philosophy is pragmatic, first and foremost. The objective is a shared product that each contributor can tailor and customize.
Uncontrolled customization can, of course, lead to incompatibile implementations. To prevent this, the AOSP also maintains the Android Compatibility Program, which spells out what it means to be "Android compatible", and what is required of device builders to achieve that status. Anyone can (and will!) use the Android source code for any purpose, and we welcome all such uses. However, in order to take part in the shared ecosystem that we are building around Android, device builders can take advantage of the Compatibility Program.
Though Android consists of multiple sub-projects, this is strictly a project-management technique. We view and manage Android as a single, holistic software product, not a "distribution", specification, or collection of replaceable parts. Conceptually, our notion is that device builders port Android to a device; they don't implement a specification or curate a distribution.
We know that quality does not come without hard work. The members of the Android Open Source Project have contributed full-time engineers, product managers, UI designers, Quality Assurance, and all the other roles required to launch modern devices in the modern marketplace. We integrate the open source administration and maintenance into the larger product development cycle.
In a nutshell:
To meet our goals, Android needs to achieve widespread, compatible adoption. We believe that the best way to accomplish that is to make sure that we ship high-quality, flagship devices with an intense product and end-user focus. The "next release" of Android is driven by the product needs for the next generation of mobile devices; the resulting excellent product is then released to open source and becomes the new current version of the platform.