From Avisynth wiki
This section contains basic information about the AviSynth script language. It presents the fundamental properties and elements of the language and the ways that can be combined to build an AviSynth script.
- Grammar - The grammar of AviSynth script language. An introduction to AviSynth scripting.
- Language elements - The building blocks of AviSynth scripts: variables, types, operators and the like.
- Script variables - How to declare and use variables in your scripts.
- Operators - Available operators for each type of variables and their relative precedence.
- Clip properties - Functions that return a property of a clip.
- Control structures - Language constructs for controlling the script flow.
- Internal functions - Ready-made non-clip functions to use in your scripts.
- User defined script functions - How to define and use your own custom functions in AviSynth scripts.
- Plugins - How to load plugins (AviSynth, VirtualDub, VFAPI and C-plugins). Plugin autoloading and name-precedence.
- Libraries -
- Runtime environment - Scripting on a per clip frame basis.