[otrs] Types of Notes

By default, or at least as far as I can tell ;-), only one type of note is set to active (note-internal). Is there any functional difference among the various types of notes (note-external, note-report, etc.)? For example, can customers see external notes, but not internal ones? If so, is it configurable as to who can see which types of notes? If so, how? Seems I recall reading something about this in the manual, but I can't find it now. All references to particular portions of the documentation humbly accepted and greatly appreciated.