The paladin is what's known as a hybrid class. They do not excel in any particular area but paladins can do moderate damage and are good healers. They are extremely difficult to kill because of their shields, heals, and their ability to wear heavy plate armor. A Paladin is usually called upon to fill the gaps in groups because the paladin can spec in different talent trees making them better at healing, protecting, or dealing damage. Because of some recent changes to the paladin talent trees, it is said that they can now tank in groups as well.

Usually the paladins are the ones who are salvaged during wipes by using Divine Intervention or another player using a soulstones on them, this is helpful because the paladin has the ability to resurrect slain players in battle.

Their ability to heal is not as effective as the other healing classes but they are still very mana efficient and more of an endurance healing class.
What's great about being a paladin is you are a hybrid class and that means you have the ability to perform better in different areas such as healing, tanking, or damage dealing, depending on how you spend your talent points. But being great at all three, however, is not likely. It is possible to be good at all of them but there will always be some other class or another properly speced paladin that can outperform you.

Low level PvP is great for paladins. A twinked Retribution Paladin is one of the strongest classes during the lower level brackets. The damage is awesome and you already have shields and heals in your arsenal. At higher levels the damage doesn't quite compare to that of the rogues or casters. The paladin's job then becomes healing, buffing other players, cleansing, judging the enemy, and attacking when you get the chance. Paladin basically becomes a defensive support class.

In raids, paladins become very useful by giving the group performance enhancing buffs. A list of their 'buffs' is listed below.

Available races which can be Paladins are: Humans, Dwarves, Blood Elves, and Draenei