Examples of usage:

• user registration via web form
• user sync with a with a different system
• exporting a specific user query via XML

REST API for users:
http://docs.easyredmine.apiary.io/#reference/users

REST API for user groups:
http://docs.easyredmine.apiary.io/#reference/user-groups

REST API for user types:
http://docs.easyredmine.apiary.io/#reference/user-types

Project membership:
http://docs.easyredmine.apiary.io/#reference/project-memberships