Picking a realm is the first choice you will make after installing World of Warcraft on your computer. Folks have plenty of different opinions about which realm type provides the best WoW experience. It's almost a personal religion for some players. The final decision about what you prefer will, of course, be up to you.
Player versus Environment (PVE)
On a PVE realm, you are never forced into a player-versus-player situation. If you choose, you can activate your PVP flag, which will allow the opposing faction to attack you. That is strictly optional.
If you are looking to enjoy a leisurely grind and don't want to deal with the war in Warcraft, then roll on this kind of realm. You may still PVP in Battlegrounds, so the PVP aspect of the game is not completely lost -- it is just controlled and tightly focused.
Player versus Player (PVP)
A PVP realm is exactly like a PVE realm in almost every way. Same dungeons, spells, mobs and areas. Even the same Battlegrounds. The only difference? Once you leave territories controlled by your faction, you are fair game for PVP.
In the starting areas, you are protected and your PVP flag is off. Once you leave the starting areas, however, you can be attacked anywhere, at any time. To a lot of players, this adds to the excitement of the grind. However, there are some things you should consider.
You will get ganked. A level 35 can kill a level 24 on sight, and it is his right to do so. A level 60 will sneak to a newbie zone and destroy any level 10 who turned on his PVP flag. You will hear the philosophy "if it's red, it's dead" thrown about a bit. Players of the opposing faction have their names in red when flagged for PVP, so if someone sees another player with a red name, they will frequently be killed regardless of level or situation.
Don't ever expect a fair fight. If you are engaged on two mobs, don't expect the other players to show you mercy. If members of the opposing faction sees you in that vulnerable position, they could very well take advantage.
You will get camped. Someone 15 levels above you will sit on your body and kill you again and again. This doesn't happen all the time or even a majority of the time, but it does happen. Is that person being a bit of a jerk? Probably. Is it within the rules of a PVP server? Absolutely. Will you get anywhere by complaining about it in the chat channels or forums? No.
Camping and ganking are all part of the WoW PVP server experience. The guy who is ganking you was probably ganked a thousand times on his way to 60. Don't let that scare you off from a PVP server. Once you get in a guild, you can call some friends to help you when you are being camped.
These servers are the place to find like-minded roleplayers. If you want to portray a Dwarf during your interactions with others, these are the realms for you. This is where you can tell stories, act in character, and find other players to engage in RP.
Roleplay Player versus Player (RP-PVP)
Finally, we have the most rare choice, the RP-PVP realm. These servers are exactly like a PVP server in every way, except it is also a role playing server. You can both roleplay with other folks and engage in all the exciting action from a PVP realm.
How to choose your specific realm
Once you know what kind of realm you want, choose which specific realm you want. Some realms have been around since launch, have tons of guilds in the high-end raid dungeons and are bursting at the seams with players. Other realms are newer, have fewer raiding guilds and have rather sparse populations. Most realms are somewhere in between. How do you discover which realms are which?
As you progress in your expertise and levels, you'll get a more refined idea of what you're after. Don't be afraid to try out different realms and different guilds; eventually, you'll find the right niche for you.
It is a little footwork
Jumping around realms and guilds definitely involves a little footwork. But, if you do a little research, you will be much happier with your realm choice in the long run.
Visit the WoW Rookie Guide for links to everything you need to get started as a new player, from how to control your character and camera angles when you're just starting out, to learning how to tank, getting up to speed for heroics and even how to win Tol Barad.