). Also, Guild Wars actively sabotages tank&nuke strategy, because melee characters do tonnes of damage (unless you try to tank, which will gimp their damage output) and because even in PvE, monsters run away from area damage (especially area damage over time - if you play elementalist, Firestorm is a LOT worse than it looks on paper). Besides, even a barely competent protection monk will buff -any- party member to the damage-absorbing ability of a large rock, in a much better way than just having a thick armor will. Read description of a [Spirit Bond] for an example.With that in mind, front line is dealing high damage, midline primarily shuts down the monsters, but they can help with damage dealing, while backline takes care of the defence. The easiest way to tell: fronline targets monsters from close range for attacks and spells, midline targets monsters from long range, and backline targets party members.
That said, professions do tend toward certain positions.
Warrior, Dervish: normally frontline
Assassin: despite the fact that they are melee, they are correctly played as midliners. You teleport or run in, kill or shutdown the priority target, then run away
Rangers: Midline. Some gimmick builds use rangers as frontliners (with warrior or dervish secondaries), both in PvP and PvE.
Paragons: Midline. They're primarily defense, but they need to attack and gather adrenaline to power the shouts
Mesmers, Elementalists, Necros: Midline. Some gimmick builds use them as backliners (with Ritualist or Monk secondaries) due to the bonuses to spellcasting. There are also (rarely used) mesmer frontline builds with [Illusionary Weaponry] skill. Note that elementalists have best snaring and best anti-physical counters in the game - it's a shame to use them as pure nukers

Monks: Backliners or midliners. Monks that use Smiting Prayers play midline, and are becoming common in PvP lately.
Ritualists: Backline, midline, sometimes even frontline (using [Spirit's Strength]). They're meant to be jacks of all trades, but they have their very unique style of playing.
The only thing you can't change about your character is your primary profession. You can change secondaries, attributes and skills at will, and it's a good idea to experiment often and pay attention to what works. Also see http://pvxwiki.com for the common, established builds.

