WoW is a major game, way more major comparing to Runescape, You start out by making a character, out of 2 'Nations' so say, Horde or Alliance.
While those -- separate into different races:
Alliance: Gnome, Night elf, Human, Dwarf, Draenei* (Draenei is only available in burning crusade)
Horde: Orc, Troll, Undead, Tuaren, Blood Elf* (Only Awailable in Burning Crusade)
meanwhile these separate into different Classes:
(forgive me if i am missing anything in classes, and if i am, tell me, i will edit)
Gnome: Warrior, Warlock, Mage, Rogue.
Night Elf: Warrior, Priest, Druid, Rogue, Hunter.
Human: Warrior, Palladin, Rogue, Mage, Warlock, Priest.
Dwarf: Warrior, Palladin, Hunter, Priest, Rogue
Draenei: Warrior, Palladin, Shamman, Priest, Mage, Hunter
Orc: Warrior, Warlock, Hunter, Rogue, Shamman
Troll: Warrior, Rogue, Hunter, Mage, Priest, Shamman
Undead: Warrior, Rogue, Priest, Warlock
Tauren: Warrior, Hunter, Shamman, Druid
Blood Elf: Palladin, Hunter, Rogue, Mage, Priest, Warlock
All Races also have ratial Ability, for example, Dwarves can detect gold, Humans can see through stealth, Blood Elfs take away mana.
The whole area is about 40-50 times more then whole RS, Imagine, Whole RS is probably less then 1 zone in WoW in size, it is separated into 2 continents, one is mostly alliance, another is mostly horde.
as you can see this map shows the ways from one place to another on zeplin or ship.Darnassus is Night Elf main city, Stormwind Is human main city, Ironforge is dwarves & gnomes (this map is older but there are 2 more cities Exodar and Silvermoon), for Horde, there is undercity for Undead, Ogrimar for Orcs, Thunderbluff for taurens.
The Point of World of Warcraft from Blizzards view was a continuation of Warcfrat Series.
In warcraft Series, It starts out as a war of Humans and Orcs, while the idiots fight, a gate opens, yes, it's burning legion, one profit saw that day, and he tried to save everyone, Thrall (current leader of Orcs in Ogrimar) being a shamman, listened to the Profit and lead his race to the other land (thus the separation of 2 lands) while humans, did not listen to him, (Ruins of Lordaeron is undercity)and eventually, Undead, Turning more humans undead and gaining a huger and huger army by the second, was not to be stopped, but Prince Arthus did not care, he eliminated more and more humans that are to be turned to scourge, eventually, his heart became cold and all he cared about is killing a demon that was doing all the biddings of the lord, he took Frostmorn (a powerfull sword, WHICH IS the voice of the lord of Burning Legion, eventually, Arthus killed his father, and lead loarderon to complete death, there were humans that tried to stop him by making an Ashbringer ( a powerfull sword that DROPS in WoW) but nothing was saved, everything in Loarderon was ruined... Arthus and Kel-thuzad opened a dark portal, the gate to Burning Legion was open, thousands of demons, comming through, destroying everything, Humans, Orcs and Nightelves had no chance, but Nightelves, Sacrafising their Iternal life Tree, Banished the Lord of Burning Legion out of the land and overpowered the rest of demons, that is how the storry unwrapped.... WoW only takes place 4 years later, surprisingly.
On WoW, Ever since the begining of the game, you get to do Instances, for horde first instance is at level 13 and its called RFC, a simple instance where you kill mob by mob, easily done, then comes WC and VC, WC is Wailing Caverns, technicaly an instance turning druids dark and wanting to raise their dark lord up, VC, stands for VanCleef, the last boss of that instance, VanCleef was designing Cathedral for Stormwind City, never gotten payed for building int, VC went outraged and decided to make a ship that would destroy stormwind completely. Then Goes RFK, Gnomer, RFK is technicaly just a place with demon boars, something left over from Burning Legion, Gnomergan is an instance where the actual Gnome City used to stand, Eventualy, some Gas broke out, making gnomes go mad, some survived, some stayed there plagued, with their plagued king, then comes SM, Scarlet Monastary is place near Dead Loarderon (Undercity) where all the holy palladins and warriors grouped and fought off the scourge (The Leader of the SM made Ashbringer) its a lvl 30-45 instance (sm) with 4 sections, technicaly, the people in SM live in denial, they belive that everyone who dares to step on their land is Scourge. Then comes RFD (lich kings Kel-Thuzad's left hand partner boss lives down there). Then comes Zul Farak, a Place where a cursed sword was burried and Trolls keep protecting it and on and on and on.
Most instances are done as 5 man group, usually, 1 tank 1 healer, 1 offhealer/DPS, 2 DPS, that group is likely to succed if classes are different and they have crowd control (such as sap, sheep etc).
I'll Edit more in later, gotta play some RS :|