The complete reference of the REST API resources can be found in the specifications: https://github.com/ezsystems/ezpublish-kernel/blob/master/doc/specifications/rest/REST-API-V2.rst. That file is actually more up-to-date than this documentation, as it is used as a development spec / reference. One problem is that it references the whole API, which isn't actually completely implemented. Some resources are still being worked on, but you should have most of what you need.
A more detailed description of the current implementation status will be added to this documentation soon.
Resources are grouped by chapters: Content, Content Types and User. In each of those chapters, you will first get an overview, with a table crossing every resource with every applicable HTTP verb, and giving you a summary of the action.
Then throughout the chapter, grouped into sub-chapters, detailed documentation for every resource, with: