Here is a basic overview. I used information from other articles that I no longer remember the source of sadly. Use this just as a starter place. Over time some things have changed and depending on what expansion you are playing, the usefulness of the various classes will change.
Fighters - main stat is strength All are tanks - absorb damage, some are good at DPS some aren't so good at it
Warrior Type - plate armor
Animalist Type Has pets
Shaper Type Has a pet (construct) can heal some
Enchanter Type pet classes and crowd control specialists
Fighters - main stat is strength All are tanks - absorb damage, some are good at DPS some aren't so good at it
Warrior Type - plate armor
- Guardian Known for having the largest health pools, largest immediate threat generation and lowest DPS, Guardians have buffers meant to help protect other classes, defense-focused, generally fight with a weapon and shield and has great single-target threat generation tools and desperation defense abilities, and the best damage mitigation in the game
- Berserker Known for being DPS tanks, Berskers have more AOEs, more offensive-minded, better AoE threat generation and will mostly build threat via DPS, generally fighting with two weapons
- Paladin A hybrid class of sorts, with threat-over-time capabilities and threat transfers, along with some limited group healing and respectable DPS, some healing and warding ability, but not to the extent of being able to serve as a main healer in dungeon content, although they can off-heal and may suffice for a lot of open-world group content
- Shadowknight Possibly the highest DPS of the tanks, SKs are known for their self-healing DPS, threat-over-time and ability to feign death, solid debuffs and damage buffs and do better DPS but lack the Paladin’s ability to heal others, although they have the ability to self-heal through vampiric abilities.
- Monk Another DPS tank that wears leather armor and relies on their Avoidance and limited self-healing to make up for their lack of plate, better sustained DPS
- Bruiser Arguably higher DPS than a Monk; still a leather DPS tank that relies heavily on Avoidance, better burst damage, have more stuns and knockdowns but have longer cooldowns
Animalist Type Has pets
- Beastlord DPS - A pet class, also widely considered among the highest DPS. This class relies on its pet Warder and knuckle/melee and thrown weapons similiar to the Monk and Bruiser tank classes, group heals, power regen/buffs
- Troubador Scout-based buff bot. Troubadors have songs/buffs that really benefit mages in the same group; offensively the Troubador brings some limited stuns and charms to enemies, along with limited direct damage spells, Troubadors have better caster buffs and have some mez and charm abilities that can be used to take control of opposing mobs. Will accompany Mages
- Dirge Scout-based buff bot counterpart to the Troubador. Generally allowing for a more active playstyle than the Troubador, the Dirge also brings songs/buffs that really benefit melee classes in the same group or raid. Offensively, the Dirge hosts a lot of debuffs against enemies as well as a few limited damage over time spells, better at buffing melee classes and can do lifetaps to siphon away enemy health. Will accompany melee types such as fighters.
- Ranger DPS - The highest ranged DPS of the scout tree; what the Assassin does with melee weapons to the back, the Ranger does with arrows from...well, anywhere, Ranger is quite good at kiting where there’s room.
- Assassin DPS - "Tier 1" DPS; generally considered among the top of the food chain, this class accounts for its DPS through stealth, stabs and poisons, most dependent of all the Scouts on proper positioning and has some excellent aggro management abilities
- Swashbuckler DPS - the Swashbuckler is a type of Scout DPS that can actually tank somewhat.Swashbucklers have very high DPS and even some threat-generating capabilities. can debuff enemies’ offensive abilities, has some token AoE ability and is less dependent on positional damage than most Scouts,
- Brigand DPS - lends itself to high damage output by way of large debuffs against a mob, leaving it vulnerable to all sorts of pointy things (as well as magic, etc. from groupmates!), Brigand debuffs enemy defenses and has a lot of stun and show-your-back ability
Shaper Type Has a pet (construct) can heal some
- Channeler a leather armor wearing, bow wielding healer. They use a pet called a Construct to absorb damage for a group member.
- Fury fast-casting heal-over-times that are marginally less healing than those of the Warden; however, the Fury possesses a number of impressive direct damage and encounter nukes, Fury is more of a ranged caster and has an edge in DPS
- Warden fast-casting heal-over-times that are marginally better healing than those of the Fury; however, instead of large damage spells, the Warden posses a number of limited crowd-control capabilities such as a root, is more melee-oriented and a somewhat stronger healer
- Templar slow-casting but very large reactive heals; lots of buffs to elemental and physical resistances for group/raid members, Templars have a variety of healing tools including reactive heals that proc when the target takes damage. Their DPS output in considered poor, and while they can be competent soloers in the right hands, you’ll likely need to do a lot of self-healing to make them effective.
- Inquisitor not-quite-as-slow-casting but not as large reactive heals as the Templar; lots of buffs to group damage output and enemy debuffs, Inquisitors also have a variety of healing tools, with an emphasis on reactive heals and debuffs, and can spec into a very desirable soloing configuration with good DPS.
- Mystic ward-based healer with some light direct-damage elemental spells, higher burst
- Defiler ward-based healer with debuffs and some light direct-damage noxious spells, more DoTs
Enchanter Type pet classes and crowd control specialists
- Coercer Mage-based crowd-control that generally takes place in the form of completely taking control of an enemy (allowing the Coercer to use them as a combat pet), or stunlocking them into oblivion. Buffs from the Coercer seem to favor the melee classes. They don’t get a regular pet, instead charms a mob and controls it. This offers great versatility, as you can pick from brute mobs, caster mobs, healer mobs, or whatever depending on the zone you’re in, but the trick to playing them is that their control over their pet will break – sometimes at the worst possible time. Instead of buffs they have reactive debuffs and damaging spells.
- Illusionist Mage-based crowd-control extraordinare! Along with that comes greatly enhanced in-combat power regeneration and a host of other goodies that fellow mages will love, Illusionist’s pet is an illusionary duplicate of the caster, and can cast all the spells the caster can. Nobody can lock down an opposing mob like an Illusionist; they’re tricky to play but unmatched soloists in the hands of a skilled player, and they have excellent group buffs, will accompany mages
- Conjurer A Mage-based pet class; very high DPS in later levels, the pets of this class are either a Tank (Guardian-based), a Mage (Wizard-based) or a Scout (Ranger-based), Conjurors do more AoE damage
- Necromancer Another Mage-based pet class that is very high DPS in later levels. The pets of this class differ from the Conjurer in looks and the fact they are Berserker-based for the Tank, Warlock-based for the Mage, and Assassin-based for the Scout, Necros have more DoTs
- Wizard DPS - One of the two highest DPS mages, the Wizard focuses on single-targets, but it's damage-dealing capabilities are just as staggering as the Warlock or Assassin, more single-tick, single-target damage
- Warlock DPS - One of the two highest DPS classes in the Mage tree, the Warlock is primarily suited for massive DPS against groups of enemies (typically encounters and some AOE), more DoTs and AoE DPS.