Welcome to the forum!
I'll apologise now that my reply probably isn't going to give you much comfort.
Isn't there a law where they have to explain what is being issued? And can't just leave, . . . . .
The problem here seems to be that a Criminal Law had already been broken. By you. Although it will probably be (just) one of the Railway Laws, which could just land you with a criminal conviction for what you have done, there is a slight hint in your explanation about the reasons, which might just lead to a more serious prosecution under the Fraud Act.
My point here, is that the Inspector had good reason to believe that an Offence had occurred and was gathering evidence. There isn't much ground for you now, after the event, to find fault with the Inspector's procedure.
To help you to understand why I suspect that this might be serious, is your explanation that you did this regularly and deliberately, for a reason which the Railway Company will not and cannot consider. It is no business of a Railway Company to be concerned with your education or how you get there - they would presume that if you cannot afford to use their offering then you would choose to use some other facility (e.g. home learning, cycling, change of college, walking, etc.)
My concern is that if you had explained to the Inspector what you have posted on here, then some Railway Companies might consider the Inspector's report (the MG11 form) as the basis for a Fraud prosecution.
No one on here can predict the ooutcome for you, but a lot depends on which Company it was and what is in that written report. Some Companies have a quite predictable process, and others not.
Anyway the guy who wrote it out didn't explain anything about what he was giving me or what i'm supposed to do.
You are not 'supposed to do' anything now. It is for the Company to decide what they will do. If you'd admitted that you routinely defraud them of the fare due for the travel you have taken, then I'll guess that (whichever Company it was) they will get back to you at some point in the future. They'll give you some options of what to do then, and I encourage you to come back here then and let us know how we can advise you when replying to the letter.
Sorry.