Alcoholics Anonymous is a worldwide fellowship that is open to any alcoholic and is there to help them overcome alcoholism. The main purpose and mission of Alcoholics Anonymous members are to stay sober and help others achieve sobriety. So that even when someone has overcome their addiction, they stay within the fellowship and help others overcome their addiction, and this also keeps them from relapsing.
There are several principles, which are found in the philosophy of Alcoholics Anonymous. One of the basic parts of its philosophy is anonymity. It is actually a big part of the program when people join an AA group; they keep their anonymity from beginning to end. There is also the concept of leading by example, which is very strong within the fellowship. It is through friendship and support that all members help each other attain and maintain sobriety.
There is another pillar of the Alcoholics Anonymous philosophy, and that is the 'one day at a time' principle. This basically means that within the fellowship, it is not promoted that one should stay sober for the rest of his, but rather, for the next 24 hours. This is often easier to confront for newcomers who want to get sober, and so they are always striving to stay sober for 24 hours. This has worked for many people and also makes it easier to help other alcoholics in the fellowship.
Those are the basics of the philosophy and mission of Alcoholics Anonymous.