If you like to PvP, choose the bloodlust battlegroup.
A battlegroup is a group of realms that pvp together.
When you do a battleground(PvPing), you get to fight against people from your own battlegroup.
If you want to start the game, you'd need to buy a $20 cd.
When you hit level 60, you'd need to buy another $20 cd.
And finally, when you hit 70, you'll need to buy a $40 cd.
WoW is vastly different from runescape.
It's a lot harder to explain, so if you want to, just use a 10 day free trial.
Trials don't get as much as paid characters (Can't trade, can't invite to party)