Guest Access
You have the choice of allowing "guests" into your course
People can log in as guests using the "Login as a guest" button on the login screen.
Guests have "read-only" access - meaning they can't leave any posts or otherwise mess up the course for real students.
This can be handy when you want to let a colleague in to look around at your work, or to let students see a course before they have decided to enrol.
If you also set an enrolment key (usually a good idea), then the guest user will be challenged to provide the enrolment key EVERY TIME they log in to the course.