Fluxus is an environment which allows you to quickly make live animation and audio programs, and change them constantly and flexibly. This idea of constant change is where the name Fluxus comes from.
Fluxus does this with the aid of the Scheme programming language, which is designed for flexibility and an interface which only needs to provide you with program code floating above the resulting visual output. This interface enables Fluxus to be used for live-coding. Most users of Fluxus are naturally live-coders and some write Fluxus scripts in front of audiences, as well as using it to rapidly prototype and design new programs for performance and art installation.
This emphasis on live coding, rapid prototyping and quick feedback also make Fluxus fun for learning computer animation, graphics and programming and is often used in workshops exploring these themes.
This manual is organized in terms of the basic topics you need to know first and more advanced topics later on, but it's not too strict, so I'd recommend jumping around to parts that interest you.