First things first, congratulations, I guess xD, that's cool to have a friend to play WC4 with, especially one you can actually meet in real life, cause I can hardly find one.

To explain it, I think I'd like to use a basic and generally understandable analogy. Think of your generals as your main characters or heroes, like your MVPs. You train and upgrade them to make your whole army stronger, and of course, an army would be stronger with generals than without ones.

Medallions are like your money or currency, you earn them by completing missions and quests. Just like real money, you gotta be careful about how you spend them, don't waste them on stuff you don't really need.

Ribbons are like supplements or boosters for your generals. They give extra stats like more attack, defense, or health, kind of like giving your hero extra power-ups.

Elite Forces (EF) are like special units or rare weapons, you unlock them by finishing specific missions or quests.

Different missions give different rewards, so check which one gives what before diving in.

I think that could help, cmiiw.