Q: What is the difference between a commercial and a free mmorpg ?

A: a free mmorpg means that you do not have to pay for play. A commercial mmorpg like world of warcraft will cost you a monthy fee between 10$-25$.

Most MMORPG offers microtransactions

At first microtransactions were just used as an alternative business model for smaller games. Instead of paying an advance sum for the game, plus signing up for a monthly subscription, the game company offers you the game to download for free, and you can play for free as well. But then you'll encounter some obstacles to progress, and are offered a way out by buying virtual stuff from the item shop. If you consider time spent without virtual rewards in a game to be a loss, then it makes sense to buy a scroll that doubles your rate of advancement. It makes even more sense to buy the reward you could get by playing directly, even if that reward is just a mount or a pet. Then somebody noticed that the two business models of monthly subscriptions and microtransactions aren't mutually exclusive. Now games like Champions Online, and since recently even World of Warcraft, have both. This leads to the bizarre situation that at the same time you pay the game company money to be allowed to play their game, *plus* you pay them money so you don't have to play all that much, but get the reward without the "grind" of playing. It's like first paying to enter a movie theatre, and then paying a second time to see the movie in fast forward instead of at normal speed, so you get to the end faster.

You can find The Sims private server and The Sims MMORPG server - we have some of that The Sims private servers in our top mmorpg list you just see as top 100.
Massively multiplayer online role-playing game (MMORPG) is a genre of computer role-playing games in which a very large number of players interact with one another within a virtual game world.

MMORPG includes pretty special problems. An example

Well, I started playing, and did both a dwarf commoner warrior, and an elf mage, playing them until their stories converge. First impression is that the mage is overpowered, having ranged magic dps, crowd control, and healing. As it is a lot easier to pick up various melee types for your party, playing a mage as your main guarantees you always have a healer around, plus excellent dps, which is a great tactical advantage. I'm enjoying Dragon Age: Origins very much up to now, due to combat being a lot more tactical than most MMORPGs. Even at normal difficulty setting you can't just storm into every fight on automatic settings and expect to come out alive.

As in all RPGs, players assume the role of a fictional character (often in a fantasy world), and take control over many of that characters actions.
A free mmorpg works like a free game. You can play for free but often you can buy items in a so called item shop.
MMORPGs are distinguished from single-player or small multi-player RPGs by the number of players, and by the game persistent world, usually hosted by the game publisher, which continues to exist and evolve while the player is away from the game (afk).