In case of online course, the classes can be live. Also the online courses may have the specific timeline. And this in turn helps the student to be accountable for their time and commitment towards the course.
In case of the distance learning mode, the course is pre-recorded and managed. This helps the student to access the content as per their time and convenient way.
Both these are accessible online and pretty much mode of access for such courses is the same. In India many universities make use of both the type of curriculum. And it varies based on the type of method students want to use for learning.
There are some of the offline distance learning courses that can be through mail. For example psychology courses, palmistry etc are being circulated through the mail delivery system.