Teach me how to play.

Hello to all HoMM fans! Please, teach me how to play this magnificent game from 1999; I used to play it, but without much strategy or understanding of what I was doing. You see, I'm just a newbie in this game, I understand very little, and I don't know all the words and concepts. I've browsed several websites and YouTube, but I haven't found anything really good or understandable. If I can understand some things, there are others I don't know, and I can't find information about them. I do want to learn how to play. Please be understanding and help me. Please write everything about everything, starting from the very basics, and you can attach photos to your messages; I will read and learn from them. I'm waiting for any amount of information; it's okay if the "education" turns out to be very long.