What does all this stuff mean?

Not to my knowledge, although you may always try to just type it in Paragon Wiki and see if it leads anywhere...

http://wiki.cohtitan.com/wiki/IO
http://wiki.cohtitan.com/wiki/SO
http://wiki.cohtitan.com/wiki/Inf

I'll agree with "check the wiki." Some of the abbreviations are going to depend on context, though. ("DP," for instance, could be Dual Pistols - Corruptor, Defender, and Blaster sets - or Dull Pain, a power in some melee armor sets.)

I'm sure someone's probably put up a list somewhere. Quick rundown of a few that come to mind:

ENHANCEMENTS:
TO - Training origin. Usable by anyone.
DO - Dual Origin - Twice as strong as Training Origin. Usable by two indicated origins.
SO - Single Origin - Twice as strong as DOs. Usable only by the listed origin.
IO - Invention origin - Usable by anyone, must be crafted, does not expire.
(S)HO - (Synthetic) Hamidon origin. Special reward that enhances two or more aspects of a power at SO levels (IIRC.) Dropped as a reward in the Statesman/Lord Recluse task forces, or from fighting Hamidon.
Proc - A type of enhancement that has an alternate effect (for example, "Chance for Psi damage" - when using the power, you have some percent chance to add psionic damage to the attack. Globals - such as a Stealth IO, which adds a stealth component to a travel power, aren't typically "procs" but get lumped in here as well.)

Basics:
HP - Hit points
END - Endurance. Think "mana" from other games.
DPS - Damage per Second
DPE - Damage per unit of Endurance used
DPA - Damage per Activation (of power)
SF - Strike force. A set of missions from special contacts similar to a story arc, but during which you cannot add people to the team or see other contacts.
TF - Task force. Heroside strike force.
PVP - Player vs Player.
PVE - Player vs Environment (most zones in the game.)
LRSF - Lord Recluse Strike Force. High end strike force, villainside.
STF - Statesmen Task Force.
LGTF - Lady Grey Task Force. Higher end task force, co-op, in the Rikti War Zone (RWZ)
ITF - Imperious Task Force. Located in Croatoa.
(Most others are referred to as their name - Posi/Positron, for instance.)
AE - Architect Entertainment - place to write or play player-written arcs and earn tickets you turn in for various rewards.
COx - City of x - overall reference to the game and expansions
COH - city of heroes
COV - City of villains
GR - Going Rogue.


Market:
CH - Consignment house. Generic name for both sides.
WW - Wentworths. (Hero side.)
BM - Black Market. (Villain side.)

Powersets and powers:

Most are going to be fairly obvious. Go, once more, to the WIki page dealing with Archetypes when you're reading about, say, Scrappers, and just look over the powersets. Note there are some that kind of overlap - EM, for instance, could be Energy Melee or Electrical Melee, but you'll get what they're asking by context many times. (Some will change it to, say, ElM, Elec, or something similar to avoid this.) Primary and secondary will be listed as (for instance) Fire/SS or FA/SS for a fire aura/Superstrength tank.

A few specifics -
AOE - Area of Effect - power that affects the relevant target type in a given area
PBAOE - Player based AOE. Targeted around the player.
AS - Assassin's Strike. The actual power has a different name in most Stalker primaries, but they're generally referred to this way.

Zones:
Again, one you'll have to get used to by context. Most aren't bad, but (for instance) if someone's talking about SC heroside, it could be Steel Canyon, Skyway City, or Siren's Call (a PVP zone.)

Other things:
GM - Giant monster (tougher enemy type)
AV - Archvillain. Tougher enemy type.
INF - Influence/Infamy. Money.
GDN - Global Defense Nerf - an overall power adjustment back in issue... well, way back.
ED - Enhancement Diversification - Change to enhancements where they lose effectiveness after a certain point. (Before ED, you could - for instance - slot one Accuracy/5 Damage SOs in a power for 166.5% damage. Now, at three SOs, you start getting the value reduced. The fourth is reduced further, etc. See the wiki again.)


... trying to think of any others unique to us that might throw you.

See my Guides and Tutorials

Surprisingly enough:

http://wiki.cohtitan.com/wiki/Abbreviations

Which is also MA for Mission Architect.

MA is the system, AE is the building.
(AE can also mean 'Architect Edition', the disc release which came out shortly after Issue 14, the issue which introduced Architect Entertainment and Mission Architect.)

I think you meant Cimerora there Croatoa is the home of the KHTF (Katie Hannon Task Force)

We've been saving Paragon City for eight and a half years. It's time to do it one more time.

Originally Posted by ShadowNate ;_; ?!?! What the heck is wrong with you, my god, I have never been so confused in my life!

Yes, yes I did. I have no idea why I typed Croatoa there.

See my Guides and Tutorials

The Red Caps got to your message and borked it. That's what they do. Annoying faeries!

MA is Martial Arts.

LEGION OF VALOR - Be a part of the Legend!

Seeing "Mo" in front of those means "Master Of..." which is a Task force setting where no one can die or use temp powers and you get a special badge if you succeed. So you'll see people calling for "Need 4 more for MoITF". Most Task/Strike forces don't have a "Masters Of" option.

SC is Steel Canyon. Nobody goes to Siren's Call. And Skyway City is Sky.

Originally Posted by Dispari I don't know why Dink thinks she's not as sexy as Jay was. In 5 posts she's already upstaged his entire career.

Angel Red
"We're heroes. Fighting injustice is the thing we do." ~Rebel Scum

When someone is talking about a particular powerset, they will often abbreviate all multi-word powers with just the letters, so if you don't see the abbreviation on the acronyms list, look for powerset context in the conversation, or check the player's powers.