MooTools is a compact, modular, Object-Oriented JavaScript framework designed for the intermediate to advanced JavaScript developer. It allows you to write powerful, flexible, and cross-browser code with its elegant, well documented, and coherent API.

Components

MooTools includes a number of components but not all need to be loaded for each application. Some of the component categories are:

  • Core: a collection of utility functions that all the other components require.
  • Class is MooTools base library for Class object instantiation.
  • Natives: a collection of JavaScript Native Object enhancements. The Natives add functionality, compatibility and new methods that simplify coding.
  • Element contains a slew of enhancements and compatibility to the HTML Element object.
  • Fx is an advanced effects API to animate Elements.
  • Request: provides XHR interface, Cookie, JSON, and HTML retrieval specific tools for developers to exploit.
  • Window: provides a cross-browser interface to the Client specific information, for instance window size.

Source: MooTools & Wikipedia