I am out of the loop

So i have Age of Kings with which i mostly play offline (sometimes playing via gameranger with 1-2 friends)
So can someone tell me which one is the most popular one? I mean which version
I keep seeing something about definitive edition, something about HD Ahe of empires 2... Can anyone tell me what those are? Or anything else you know of? Also if i want to multiplayer which are the official servers? Is it steam? Or what?