Monk - 3 different Forms, Raptor, Coeurl and Opo-opo. You cycle through them using different abilities for each form depending on the situation, for example: Your Demolish DOT is about to run out, so instead of using Snap Punch, you use Demolish in Coeurl form. It's all about keeping up Greased Lightning (a 3 stack attack speed buff that is granted on every Coeurl ability), and at higher level, getting Chakras to open (5 total) by critting, using it on The Forbidden Chakra ability. Very fast class, with the most positionals, but it regarded as the easiest melee.

Dragoon - Keep Blood of the Dragon up. That allows you to use the abilities Geirskogul, Fang and Claw, and Wheeling Thrust. Start with a Impulse Drive -> Disembowl -> Chaos Thrust combo. That grants you Wheeling Thrust, just thing of it as a 4 button combo (becomes 5 at lvl 64). Then do a True Thrust -> Vorpal Thrust -> Full Thrust -> Fang and Claw (granted from full thrust) combo. Pretty much the basics. Use Geirskogul, Jump, Spineshatter Drive, and Dragonfire Dive off cooldown in between globals. Use Life Surge whenever its up on Full Thrust. Use cooldowns (Blood for Blood, Dragonsight, and Battle Litany) whenever up. Dragoon is a very set in stone rotation. Doesn't change much, other than your cooldowns.

Ninja - Don't really remember the rotation, but it's opener is fucking hell. Lots of off gcd abilities to double weave in between globals. Mudras are like a fighting game combo system where you have to press them in a different 3 button combo every time (depending on which ability you want to use), and the activating it with Ninjutsu. If you fuck up, oh well. Is currently, and has been for a long time, the most desireable dps in the game. Has what is essentially this game's version of misdirect, and the best damage cooldown in the game (Trick Attack, 10% damage increase to target for 10sec).

Samurai - Has 3 Sen Rune thingies that you build up by doing 3 combos, each giving a different Sen. 1 2 and 3 Sen change the ability Iajutsu into different abilities. 1 is a dot, 2 is an aoe cone, and 3 is Midare, a super hard hitting single target ability. They also have Kenki which builds up with every weaponskill. You use kenki on Shinten which is a off global single target ability, as well as Kaiten, which increases the damage of your Iajutsu abilities. Samurai is a heavy resource management job. You're always planning out how much kenki you have, how much you need, when to use what combo, and what finisher to use.

Bard - Procs, Crit, more Crit, Procs. Highly mobile ranged job that relies heavily on Crit. You have 3 different songs that you use in a rotation, allowing you to reset cooldowns, or use abilities while they're active. Not too hard to learn, super challenging to master. No one will care if you're not the best bard ever though, since they bring some of the best buffs around. Just like Dragoon and Ninja, have been party of the meta God comp for years.

Machinist - I don't know much about them other then this. They have an ability called Wildfire that takes all the damage done in 10 sec, and does 25% of that at once. I've read multiple threads stating that they're the most clunky class to play at 70, and have a lot of double weaving between globals. They're pet AI for turrets (just like Summoner) can be really dumb as well. Some people like it though, so you never know. Was part of the meta before 4.2 made triple melee stronger, but you'll never be not taken as a Machinist. They bring almost the same utility as Bards, and output higher personal DPS.

BLM - Don't know if you're interested in this, but i'll keep it short. Explosions. Very hard to master because of low mobility and having to plan around fights more than any other job. High personal DPS with no utility (like Samurai). Easy rotation, but the complexity comes from having to know the fights inside and out. Explosions.

Red Mage - The main thing Red Mage has for it is Dual Cast. Every time you cast an ability with a cast time, your next ability is an instant cast. You use abilities which increase either your Black or White mana on your job gauge, alternating between them until you reach the top. Then you use that Black and White mana to leap into melee range, use a 3 button melee combo, then leap back out to range. Throw in a couple of cooldowns, and the fact that you're a rezbot seeing as you have instant cast rezes for days, and that's about it. Easiest class to play in the game that is highly sought after in progression for their rezzing. Lowest personal dps in the game.

Tanks (i'll try and keep this simple, as I don't know much about them).
Warriors - Hit like a truck with multiple Fel Cleaves back to back, turn into a helicopter and reck multiple mobs. Highest DPS tank, with middle of the pack utility.
Paladin - Best utility of the 3 tanks, and second highest damage. Make good main tanks.
Dark Knights - Worst dps and utility of the 3 tanks. Still viable, but might be left out of groups for the other 2 tanks.