canvas-lms/public/partials/_course_visibility_help.html

<div>
  <b>Course</b>
</div>
<div>
  All users associated with this course
</div>
<div>
  <b>Institution</b>
</div>
<div>
  All users associated with this institution
</div>
<div>
  <b>Public</b>
</div>
<div>
  Anyone with the URL
</div>