Learn English – is there any difference between ‘enroll in’ ‘enroll on’ and ‘enroll for’

"Enroll" is used to mean that you have registered for something, almost always a class or course of study. So you can be enrolled in Differential Calculus or in the Engineering Track, or enrolled at Some Fancy University. In the first usage (in), you would be on the list of people taking Differential Calculus. In the second usage (at), you would be an active student at Some Fancy University.

Neither would imply that you were actually going to class.

There are a few other uses of enroll, but they are less common. You can sometimes see it used as "add to a list of participants," as in "she enrolled in the company's health insurance program." In those cases, you can use either "joined" or "recruited" instead, depending whether the person added themselves to the list, or someone else added them to the list. "Joined" and "recruited" are more broadly applicable and will sound right in most contexts, while "enrolled" may not.

"Enrolled" also sometimes has specific meanings to some professions. You will probably never be in a situation where those specific meanings matter. In every case I am aware of though, it means some variation of "write down on a list," sometimes with very specific lists (for example, "enrollment" is the process for creating noble titles in many countries).