Distance education
The defining characteristic of all forms and generations of distance education is the separation of student and teacher in time and space. Distance education can be seen as the precursor to online learning. Before the advent of virtual universities, many higher education institutions offered some distance education through print-based correspondence courses. These courses were often referred to as a "course in a box". These have been developed so that students can obtain almost immediate feedback from professors and online tutors through e-mails or online discussions.