This page is intended as a short guide for terms used in this guide, and their implications. It is generally advised to read this to get a better grasp of how comparisons are made.
You should know these
BtH - Bonus to hit. Every point in BtH is a added to your accuracy. You can learn more about it in the Big List of AQ Formulas.
BTH Lean - Every weapon/armor/pet/guest can have a Bth lean. It can vary between being inaccurate, but powerful; neutral; and accurate, but less powerful. A -5 Bth lean means you lose 5 points off your BtH, but the damage will be multiplied by *85/(85+(-5)), which is *1.0625, meaning the damage is increased by 6.25%. Most things have a +0 Bth lean.
Armor Lean (FD/MD/N/MO/FO) - Your armor can have a damage lean, multiplying both damage received and damage taken by the lean. A Fully Offensive armor will deal *1.25 damage at the cost of taking *1.25 damage. A Fully Defensive armor will deal *0.8 damage, but only take *0.8 damage.
Special - Sometimes your weapon will perform an attack independent of your armor called Special. This attack isn't affected by your Armor Lean, and its strength is inversely correlated to its rate of occurrence, meaning the rarer a special is, the stronger it will be.
Proc - The rate at which the special occurs. A 20-proc weapon will have its special occur 20% of the time.
No-Proc - Weapons without a special. Weapons without a special should deal on average less damage, and to compensate they receive a multiplicative bonus of dealing *1.08 of their damage.
MRM - Stands for Melee, Ranged, Magic. When MRM is used, it usually refers to the "combat defenses" of either the player or the monster which is shown when you hover your mouse over either of their info-heads in the two bottom corners.
GGB - Golden Gift Box. Read about GGBs here.
FSB - Full Set Bonus. A bonus that you get from wearing all items of a set.
MC - Mastercraft. When an item is Mastercraft(ed), it has some kind of bonus. In some cases, a weapon's MC bonus is a plain +5% damage. MC bonuses always have the same value in power, regardless of what bonus it is.
Rare - If an item is rare, it means that the item is unavailable. Some items are "seasonal rare", meaning that it temporarily comes back at a specific time each year. Some items become permanently rare (often abbreviated perma-rare or alike).
AoS - Angel of Souls
BoA - Blade of Awe
BC - Blood Contract
CIT - Chieftain's Ironthorn
DB - Dragon Blade
DBurst - Destruction Burst
FGM - Fairy Godmother
PVF - Predatory Vampire Form
PWD - Powerword Die
WKZ - White Knight Z
WOS - Warlic's Oblivion Sphere (has been updated. Lvl 150 version gives +50 INT and LUK instead of +45.)