ECS is a library that can be used by any script or plugin. It is intended to be easy to use and implement. It includes several features you can easily add to your scripts without too much efforts:
ECS source code is heavily documented, so you should give it a look to familiarize yourself with. However it's not really necessary, reading this documentation should be enough. A demo script is also included, so be sure to give a look at the plugin.sk.ecs.dummy.* scripts files to see how things should work.