New game, new stats, new numbers to stack - isn't that how the story always goes?SWTOR's no different, fundamentally, from many other MMOs. Plus, to make things a little simple for the new player, each class basically has its own stat, so you won't spend a lot of time fighting with people who share your armor type - just people who share your class.
SWTOR actually does a lot better of a job recently as far as getting you used to seeing a certain stat on your gear. Early on in beta, quest rewards would sometimes offer you one stat or another, and unless you really enjoyed reading tooltips, it was kind of hard to tell what each stat actually did - so as a fledgling adventurer, you're left wondering, what stat do I want? I'm wielding a dual-bladed lightsaber - do I want Willpower or Strength? Troopers and Smugglers both use guns - but do I want Cunning or Aim? Or both? Those kind of questions naturally arose early on, but a lot of the gear from quests now passively points you in the right direction.
Here's a short rundown of what each of the stats you'll see means - most of them should look pretty familiar if you've got any MMO experience (and if you don't... welcome!).
(Reminder: this is beta, this is technically still subject to change, yadda yadda. Also my familiarity with the tank stats is pretty low; it's been my least-played role in the beta.)
Any screenshot below can be clicked to embiggen. Also, these screenshots were taken on a Smuggler, so some of the tooltips contain extra info that only applies to Smugglers (and Imperial Agents) - but it never hurts to look.
Strength - the choice of melee beatsticks everywhere. The primary stat of Jedi Knights and Sith Warriors, this increases your aptitude in melee combat. It could be considered a secondary stat for Jedi Shadows and Sith Assassins, but certainly not at the expense of their primary stat, Willpower - and finding both together on one item is rare. For those classes for whom it is a primary stat, Strength will increase the damage and crit chance of their melee abilities. Sample Item: Ascendant Warlord's Lightsaber, a weapon geared towards melee DPS.
Presence - the amazing solo stat. Presence, as you can see, enhances your companion's damage, health, and healing - it's the all-purpose companion stat. Mostly useful for soloing, but I could see it having some use if, say, you needed your companion to fill a role in a flashpoint for a missing player character. Notable in the above screenshot is that Presence is one of the few stats that doesn't increase crit chance - your companion's crit chance is improved by their own stats & gear, most likely. Sample item: Advanced Command Augment 14, which isn't actually a piece of gear so much as it is an augment to upgrade other pieces of weapons and armor.
Aim - it comes between "ready" and "fire" for a reason. Largely the purview of Republic Troopers and Bounty Hunters, this is also an occasional secondary stat for Imperial Agents and Smugglers. Aim, as it says, increases aptitude with ranged weapons, and for the troopers and hunters, it increases the damage, crit chance, and healing (yes, healing) of their abilities. Sample item: M-008 Deadeye, a ranged DPS blaster rifle. Healers would probably look to replace the accuracy with alacrity or crit rating - heals can't miss, after all.
Cunning - for those of us who use our brains... to tell us when to shoot first. Cunning is the primary stat, as you can probably tell from the info in the screenshots, of Smugglers and Imperial Agents, and a secondary stat for Troopers and Bounty Hunters. Cunning covers ranged damage/crit and tech damage/crit - and tech is what Smugglers and Agents do best. Sample item: Ace in the Hole, an off-hand blaster pistol (meant entirely for the Gunslinger class, more or less).
Endurance - it's what keeps you alive, literally. Endurance shows up on almost all your gear, and serves to increase both health and out-of-combat health regen. Everyone will get some of it pretty much by default, but the six tank specs (that's Vanguards, Powertechs, Sith Juggernauts, Jedi Guardians, Sith Assassins, and Jedi Shadows, for those of you keeping track at home) will probably want the most of it. Sample item: Ascendant Guardian's Lightsaber, a tank's lightsaber, with high amounts of endurance, a threat stat (accuracy), and a defense stat (absorption).
Willpower - for our Force-using friends. The primary stat for the Jedi Consular and Sith Inquisitor - yes, even the melee Advanced Classes in each of these! - and the (very rarely used) secondary stat for the Sith Warrior and Jedi Knight. These increase the Force damage and healing of your Consular and Inquisitor powers - and if you're a Shadow or Assassin, they'll increase your melee effectiveness too. Sample item: Ascendant Consular's Lightsaber, meant for our caster-type Force-users - the alacrity is a good indicator of this.
Expertise - the vaguest stat in the land. "Increases your effectiveness in PvP combat" - what does that mean exactly? Well, as it turns out, Expertise makes you better at everything in PvP combat, as these three screenshots show - dealing damage, healing, and resisting damage to and from other players in PvP only. Sample item: Battlemaster Combat Medic's Cannon, a trooper assault cannon meant for healers.
Power - overwhelming? Power (which can show up on items as the more generic "power" or occasionally the more specific "Force power" or "tech power") is a simple statistic that increases tech or Force powers'... power. Redundant much? Basically power makes you better at whatever it is you do - more damage, more healing. Sample item: Colicoid Watchman Scattergun, an off-hand item for Scoundrels which would improve either their damage or their healing, depending on how they've allocated talents. (The accuracy is better for damage-dealing scoundrels, though.)
Crit Rating and Surge - two closely related stats. Crit increases your crit chance, while surge increases the effect of your crits. Simple enough. Sample item: Battlemaster Force-Master's Focus, sporting both crit and surge, meant for PvP casters or healers of the Sage or Sorcerer variety.
Alacrity - it's like someone checked the thesaurus for "haste" and just used the first one they found. Alacrity increases the activation time of non-instant abilities. It does not affect the global cooldown, which seems to be constant. Sample item: Ultratech Combat Medic's Enhancer.
Accuracy - straightforward, although unfortunately lacking in good screenshottage. Accuracy helps you hit. But there's a plus side - once you pass 100% accuracy, accuracy also helps you start bypassing armor and resistance! The concept of a 'hit cap' is thus somewhat lessened - more hit will still help you do damage, even past 100% hit.
Tank Stats - sadly, I do not have a good screenshot for these, largely on account of not having any of those stats. Here's a quick rundown, though.
Shield Rating - the chance that a shield will be triggered in reaction to an attack. Shielding is useful for all tanks (even the Assassin and Shadow, who somehow have an invisible third hand to use a shield generator - maybe they're holding it with the Force).
Absorption Rating - the amount of damage absorbed when your shield activates. Easy-peasy.
Defense Rating - increases parry (turning aside ranged attacks) and deflection (turning aside ranged attacks) at an equal rate.
Resistance - applicable to any one of TOR's four damage types, which are Kinetic, Elemental, Internal, and Energy. Elemental and Internal damage bypasses armor. Kinetic and Energy do not seem to do so. If an attack doesn't say what it is, thus far, you can safely assume it's Kinetic.
Glance Rating - to be honest, I have no idea what this is. It's possible it's one of the other stats under a new name.
That just about wraps it up for stats. Special thanks to Gankstah's Tanking: A Primer - FAQs for help in deciphering the tank stats. It's a good read if you're interested in the meat and potatoes of tanking - it actually contains a good deal of the formulas for deciphering how to convert from rating to chance of resistance, shield, et cetera.