Sir_diealot Massively Multiplayer Online Role Playing Game. That’s MMORPG.
WoW is a MMORPG. It’s basically a game meant to be played with tons of people at the same time. Some of the MMORPGs are made into a huge open world like Aion/Guild Wars 2/ Wildstar or WoW and some of them are instanced like Vindictus, where you do only dungeons and raids with people. The Elder Scrolls Online: Tamriel Unlimited is also a MMORPG. Basically a “Skyrim/Oblivion” game made into a larger world where you can join with other people and do whatever you want there with them.
Now, there are few games that differ from other standard MMORPG games like WoW or Everquest or Final Fantasy 14 in terms of gameplay. Some of them are turn based, some of them are hack and slash-ish (where you mash the buttons until your fingers bleed) and some of them might be even strategy MMORPGs (which are usually rare). There is also a genre called MMOFPS (Firefall, Destiny, Warframe etc.). Same thing as MMORPG only made as a shooter.
If Witcher 3 was made for online play, it would be a MMORPG instead of just RPG. The only difference between RPG and MMORPG is just the thing that you can connect with other players and play the same game at the same time and that’s all.
I wish I could explain it to you a bit better but ehh, I’m too young. I don’t know all the English words hahah