Icecast, is a collection of programs and libraries which help to stream audio over Internet.
Icecast has three basic components they are
The server in the case of this tutorial is where the listener connects to to listen. The job of the server is to broadcast the audio data recieved from the source to the listeners. What icecast does is it streams audio to listeners.
The source is where the audio data for the server is provided from. IceS is a program that sends audio data to an icecast server to broadcast to clients. IceS can either read audio data from disk, such as from Ogg Vorbis files, or sample live audio from a sound card and encode it on the fly.
DSP stands for "Digital Signal Processing". In terms of streaming, it just sends the data to the server in digital form, and if necessary, re-encodes the data to a more suitable form (MP3, OGG, specific bitrates). It handles socket connections, timing of data etc. Libshout library is the library used for performing these functions.