CreateJS is a great suite of modular libraries and tools to make HTML5 games and other interactive applications. In the core of CreateJS, there is 4 libraries: EaselJS, SoundJS, PreloadJS, and TweenJS. These libraries are completely independent, i.e., they can be used isolated or even with other game libraries.
EaselJS is the main component of CreateJS. EaselJS controls the game loop, the event manager, the hierarchical organization of objects and the rendering system. It works above the canvas element, thus, providing an easy interface to draw shapes and bitmaps.
SoundJS provides a consistent API to use audio in different browsers. It works via plugins which abstract the actual audio implementation, so playback is possible on any platform without specific knowledge of what mechanisms are necessary to play sounds.
PreloadJS is used to preload all assets to your game, such as images, sounds, data, etc. It provides a complete API with an event system so you can track the loading progress and the connection fails.
TweenJS provides tween function for animations. It can be used independently and provide a simple but complete API to track tweening of object properties and chained commands.
Together with these four libraries, the CreateJS suite also comprises a set of tools to aid the game development process, from applications for exporting SWF animations to EaselJS spritesheets to code completion for editors.
Checkout the video below by the creator of CreateJS to have a better overview of what CreateJS is capable of.