This chapter gives you an overview of the technologies described in this book. GStreamer is a framework for creating streaming media applications. The fundamental design comes from the video pipeline at Oregon Graduate Institute, as well as some ideas from DirectShow. GStreamer's development framework makes it possible to write any streaming multimedia application. The framework includes several components to build a full featured media player capable of playing MPEG1, MPEG2, AVI, MP3, WAV, AU, ... GStreamer, however, is much more than just another media player. Its main advantages are that the pluggable components also make it possible to write a full flegded video or audio editing application. The framework is based on plug-ins that will provide the various codec and other functionality. The plugins can be connected and arranged in a pipeline. This pipeline defines the flow of the data. Pipelines can also be edited with a GUI editor and saved as XML so that pipeline libraries can be made with a minimum of effort. The GStreamer core function is to provide a framework for plugins, data flow and media type handling/negotiation. It also provides an API to write applications using the various plugins. This book is about GStreamer from a developer's point of view; it describes how to write a GStreamer application using the GStreamer libraries and tools.