Priests are pure spellcasters whose strengths are healing and defensive spells. Priest spells are divided between the holy and shadow schools, and fall into several catagories; Heal, attack spells, crowd control and buffs. While the Druid and Paladin can also heal, none are as good as priests. Priests can also resurrect a dead player, which helps in instances and the like.
I have found priests are actually a hard class to play because of the fact you don't deal a lot of damage, so the harder quests you most generally need to group with someone. Preferrably someone who deals damage, so you can sit back and cast healing spells.
