It is a method where a student is not required to be physically present in class to get an education/obtain a degree; it can be online or by correspondence. As an alternative, you can use the term unconventional education.

--------------------------------------------------
Note added at 3 hrs (2011-09-12 02:00:43 GMT)
--------------------------------------------------

I disagree to the use of the term "affiliated" as it means that a student is registered but not attending classes and it is way different from the context of the explanation offered.

التعليم عن بُعد = Distance learning أو E-learning
والطالب الذي ينتسب إلى جامعة أجنبيّة يُسمى بـ External Student
والطالب الذي ينتسب إلى جامعة محليّة يُسمى بـ Affiliated student

.