An Organization can associate a user outside of it to be a trainer of its organization simply by providing the email address of the trainer.
Associate trainers have more power than normal trainers that you add to a course.
They can create new courses in the associate organization under the condition that they remain the trainer for the course.
This way, associate trainers can create and even manage your course from beginning to the end, which generally must be done by the organization administrators.
You must trust the associate trainer who delivers the training to your standard as you will be paying for this.