So as we all know MMO RPG games are Massive Multiplayer Online Role Playing Games. These type of games are usually set in the medieval era with a few interesting twists and turns along the way. Imagine Game of Thrones mixed with Harry Potter in a game, that basically sums it up.
Now if you have never played an MMO RPG before, I will explain what each class does in the easiest way possible for you to choose your favorite:
P.S: This list will not include player created classes like in Elder Scrolls for example (where you mix your own skills to create a class out of two different ones)
Warrior / Berserker / Barbarian
Warriors are your hack and slash tanks. They take a lot of damage, they deal a lot of damage or both. They command squads and use battle shouts to enhance the stats of their team. They also use Two Handed weapons such as Battle Axes, Hammers or Greatswords.
Guardian / Paladin / Knight
Guardians are like Warriors but with Holy/Spiritual Power. They mostly use shields and books to enhance their skills. They have the ability to Tank the enemy damage or Heal the allied squad. But make no mistake, with the right build in the right game, they can out damage a Warrior with ease.
Mage / Wizard / Spellcaster
Mages are the masters of the elements. They can cast Fire Balls, Ice Blizzards, Land Slides or Thundery Hurricanes. They use Staves or Scepters to their advantage to manipulate the elements. They are usually ranged classes and can also Heal the team depending on if the game built their Ice Specialization as a support one.
Warlock / Dark Wizard / Necromancer
Warlocks are like Mages who never listened in school. They use Dark Magic to summon Demons, Minions and Plagues to torment the opponent. They are also ranged characters.
Ranger / Hunter / Trapper
Hunters are the masters of, well, hunting. They can command battle pets such as Bears, Lions, Dragons, etc. They are very cunning and can blend in with nature very well while attacking from a distance with their bow and arrow. They can also utilize traps for an ambush.
Rogue / Thief / Ninja
Rogues are the masters of Stealthy swordplay. They blend in with the shadows and uses poisoned daggers to backstab any enemy regardless of power. They are usually always on the front lines besides the Warriors and Guardians but you never see them unless it's too late. They can pick pocket your socks off your feet while you have shoes on without you even noticing it. They usually assassinate the main target of importance, like a King for example, while the front lines keeps them busy.
So there you have it. Which one is your favorite? I know that some classes are missing and will be added in the future. For now I only have the major ones in most of not every MMO RPG. Let us know which one you like the most! Also please include the game that you play your favorite class on :)