So, I have been playing WoW (World of Warcraft) for many years - I have a balance druid (explained soon) that I used to raid (end game content) with during Wrath of the Lich King (a few expansions ago) and have a fair few alts (other characters I play).
Let me get one thing across to you right now... this game can take over your life...
If you have an addictive personality then this game will consume you, don't play it! I got to that stage, spending more time on the game than I spent sleeping and eating for a section of my life when I was a student, it was a killer!
If you learn how to pace yourself, how to enjoy the experience and stick with ONE character then each expansion is a nice add on, allowing you to level to a higher point and then raid with friends, casually.
Ok different aspects to WoW.
You need to pick a server - I would recommend English Speaking PVP (player verses player) as it makes things more interesting, but you can go for PVE (player verses environment) which means the two factions can't kill each other, where as on PVP they can in certain areas.
You now need to pick a faction Alliance or Horde - traditional 'good' against traditional 'bad' - the choice is yours!
Now you need to pick a character - you will want to read bellow about this and Google some options that take your fancy!
Questing - you take on 'mission' aka 'quest' from NPC's (non playable characters) to kill or collect items or animals or people and then once complete you return to them and they give you in game money, experience and items relevant to the level of your character and the area you are questing in.
There are MANY different areas to quest in, most completely different to the one you were just in with lots of amazing landscapes, animals and quests to see, find and complete. When you start the game you are in a 'starting area' as you complete quests you move from area to area and discover new lands as you gain levels.
As you level up you begin to start being able to go into 'Dungeons' aka 'Instances' now these have harder enemies and as a team of 5 players you go in and work your way through the dungeon/instance till the end. There are better items for your char (character), money and experience. Within an instance you have a 'Tank' a character who takes all the attention of the things you are trying to kill, a 'Healer' who heals the tank and allies and then finally you have the 'DPS' (damage per second) who attack the things your killing fast, as the Tank takes there 'Argo' (attention) and the healer heals them and the DPS.
Now DPS break down further, ranged (you do damage from a distance) and Melee (you hit them close up) - My main (main character I play as) is a Balance Druid, so I do damage from a distance.
Now some classes are more versatile than others, for instance, Druids can be Tanks, Healers or DPS depending on what Talents you chose as you level up (this will be explained in game). Other classes likes Mages or Warlocks are purely DPS classes and can't ever tank or heal.
It would be worth doing some searches in Google of the different classes and seeing what takes your fancy! Some you won't be able to play as they require more recent expansion (listen bellow).
Finally when you reach the level cap (top level) which is 90 at the moment you will run JUST dungeons/instances and try to get the best gear for your character that is possible, when you have done this you then run 'Raids' which are MASSIVE dungeons/instances that drop the TOP gear in the game and make you the best and strongest character in your realm. There are updates about every 6 months releasing new Raids so there is always a new goal to reach.
Now there are TONS more things to know, but all of that you can and will find out about in the games, it is exciting and it is fun, but be warned it is addictive and people have ruined their lives playing this game!
This 'Battle Chest' will give you a month free game time (usually £8.99) and allow you to level up to level 80 - you will then need to buy World of Warcraft: Cataclysm Expansion Pack (PC/Mac DVD)
which takes you to level 85 and then World of Warcraft: Mists of Pandaria (PC DVD)
which takes you to level 90 and is the latest expansion, a new one will be out in the next two years I would have thought.
If you don't want to put your card on the WoW website to refresh your subscription each month you can buy World of Warcraft 60 Day Pre-paid Game Card (PC/Mac)
which can be nice and handy!
Finally, lots of people will try to hack your account by giving you false links in game that make you 're-sign' into the website, they do this to sell all your characters stuff, steal the Gold (in game money) and send it to their character, by the time you have logged a complaint with Blizzard (the company who run Wow) and they respond it is too late, you have lost everything. Just be careful.
Apart from that - Enjoy!
Hope all that information gives you a little bit of an idea of what WoW is all about and has wet your appetite to jump in game!