A good question.
The answer is “none”. They are all names for the same thing, and relate to learning or studying “at a distance”. In other words, without physically attending a “bricks and mortar” learning establishment.
Wikipedia says the following:
“Distance education as a generic term used to define the field, or distance learning, is a mode of delivering education and instruction, often on an individual basis, to students who are not physically present in a traditional setting such as a classroom. Distance learning provides “access to learning when the source of information and the learners are separated by time and distance, or both.”
Distance education courses that require a physical on-site presence for any reason (excluding taking examinations) may be referred to as hybrid or blended courses of study. Massive open online courses (MOOCs), aimed at large-scale interactive participation and open access via the web or other network technologies, are recent developments in distance education. A number of other terms (distributed learning, e-learning, online learning, etc.) are used roughly synonymously with distance education. However distance is the oldest and mostly commonly used term globally. It is also the broadest term and has the largest collection of related research articles.”
There is also some interesting historical content attached to the Wikipedia entry, which you may be inclined to have a look at.
Simply type “distance education” into the Wikipedia search box, or go to the universal search engine Google and do the same thing.
The first or second (depending on where you are geographically situated) clickable link in the organic listing on Google takes you to the full Wikipedia entry.