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.
Going back to school (which is what studying of any kind can feel like, particularly if it’s been some time since you did any) can be a challenge for some people. But don’t let it put you off.
It’s broadly accepted that education contributes to the defeat of poverty.