MPEG-4 is so broad an overview article ends up being very difficult to write. The best a newcomer can hope for is an incremental study until the pieces begin to fit together. The articles below are good starting points.
A short overview of MPEG-4 for the System Architect by Streamcrest's Robert Bleidt. Also useful for marketing people. This issue also contained other invited articles on MPEG-4.
A regularly updated technical summary of all aspects of the MPEG-4 standard. Many additional technical tutorial documents are available on the MPEGIF (MPEG Industry Forum) website.