Other than University or school (I'm not in Uni yet), where can I learn accurate, detailed and accessible medieval European history as a whole ad learn about the various empires, kingdoms, etc from the fall of Rome to the end of the Middle Ages? For example, to define my understanding of the Holy Roman Empire versus other medieval empires, etc.
I prefer any online sources (videos, texts) and/or books (textbooks are fine) from which I can learn all this. Thank you so much!
Well, Medieval Europe is a big place. Are there any particular things you're interested in?
Anyway, we have a Booklist here you may find helpful. The Medieval section is a bit of a mess right now, (There's some talk amongst the Medieval Flairs of a redesign, but that takes time.) but there's still plenty of useful stuff in there.
In addition, here are some specific recommendations
Medieval Europe, by Chris Wickham: If you want a good, solid overview of the whole period, this is where to start. Easy, accessible, and solid scholarship.
The Norton Anthology of English Literature, Volume A: The Middle Ages. This is the go to undergrad textbook for Medieval Literature. It has loads of important stuff you need to read if you're interested in Medieval Lit, and it has loads of glosses, notes, and contextual passages to help you understand things. I'm not the biggest fan of Norton's Critical Editions, but the anthologies are fine. This volume has the upside of being extremely cheap: You can pick it up for about $7 on Amazon.
A Time Traveler's Guide to Medieval Europe, by Ian Mortimer: An excellent resource for the daily life of Medieval People: what they ate, how they lived, and so on.
The Crusades: The War for the Holy Land, by Thomas Asbridge: Asbridge is a good writer, and an accomplished historian. I feel safe recommending any of his books, though this is the only one I've read
If you can give me more specific feedback on your interests, I'd be happy to suggest more books in the area!